Howscreeningis Setupand Themidwife'sroleandresponsibilities 205

CHAPTER11

Antenatalscreeningofthemotherandfetus

LucyKean,AngieGodfrey,AmandaSullivan

CHAPTERCONTENTS

Screeningprinciples204

Limitationsofscreening204

Socialandpsychological impactofscreeninginvestigations204

Howscreeningis setupand themidwife'sroleandresponsibilities205

Documentation205Discussionofoptions206Theprocessofconsent206

Issues toconsiderwhenpresenting information207

Explainingrisk207

Individualscreeningtest considerations208

Fetalscreeningtests208

ScreeningforDownsyndrome208Screeningforhaemoglobinopathies210Ultrasonographyforfetal screening211Newandemergingtechnologies214

Screeningfor maternalconditions214

Infectiousdiseases214

Newscreening215

Mid-streamurinetesting215Screeningforredcellantibodies216Howthe resultsarepresented216Whatparentsneedtoknow216

Managementwhenanantibodyisdetected216

On-goingsurveillance217

Conclusion217

References217

Furtherreading219

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Usefulwebsites219

Screeninghas nowbecomesucharoutinepartofantenatalcarethatmanywomenacceptthis,oftenwith little thought.Thereis noaspectofthescreeningprogrammethatdoesnot,however,havethepotentialtoraisehugesocial,emotionalandhealthissuesforpregnantwomen.Theroleofthemidwifeistoguidewomen through thewealth oftestsavailable,withthebestadvicepossible.This canonly be achievedby excellenttraining andregularupdatesfor allmidwivesanddoctors.Screening developsandmovesforwardevery fewmonthsand so vigilanceonbehalfofusall isneededto ensureweprovidethebestcare.

Thechapteraimsto:

•discusstheprinciplesofscreening,goodcounselingtechniquesandthepotential impactofpositive resultsonwomen

•describethecurrentlyavailablescreeningtests,theiraims,andtheefficiencyofeachtest

•definewhatconsentisandhowtheconsentprocessshouldbeundertaken

•provide informationregardinghowto dealwithpositivetestsandwhatnegative resultsmean.

Screeningprinciples

Screeningofamotherandbabyisnowamajorpartofcareforallpregnancies.Theunderlyingprinciplesofscreeningarethattheconditionbeingscreenedformustbeimportantandwellunderstood(i.e.somethingthatmakesadifferencetohealthandwellbeing and doesmoregoodthanharm).Treatmentshouldbeavailableand atastagewheretheoutcomecanbechanged.Thereshouldbeanappropriateandacceptabletestthatisavailabletoadefinedgroup,makingthescreeningcosteffectiveinreducingpoorerhealthoutcomes.

The National Screening Commifee of the United Kingdom (NSC 2013) definesscreeningas:

aprocessofidentifyingapparentlyhealthypeoplewhomaybeatanincreasedriskofadiseaseorcondition,theycanthenbeofferedinformation,furthertestsandappropriatetreatment to reduce their riskand/oranycomplicationsarisingfromthedisease or condition.

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Broadlyspeaking,theconditionsthatformthenationalprogrammeforscreeningintheUnitedKingdom(UK)meetthesecriteria.Whenscreeningforcurrentlyunscreenedconditionsisconsidered(e.g.GroupBstreptococcus),itisweighedagainsttheseimportantcriteria.

Screeninginpregnancycanbedividedintolookingforconditionsinthemotherthat,ifuntreatedorundetected,couldaffectherhealthorthehealthofthebabyorboth,andscreeningforconditionsinthefetusthatcouldimpactsignificantlyonthehealthofthebaby.

Limitationsofscreening

Screeninghasimportantethicaldifferencesfromclinicalpracticeasthehealthserviceistargetingapparentlyhealthypeople,offeringtohelpindividuals tomakebetterinformedchoicesabouttheirhealth.Therearerisksinvolved,however,anditisimportantthatpeoplehaverealisticexpectationsofwhatascreeningprogrammecandeliver.

Whilescreeninghasthepotentialtosavelivesorimprovelifethroughearlydiagnosisofseriousconditions,itisnotafoolproofprocess.Equally,somescreeningisdirectedatdetectingconditionsinthefetusthatmayleadtosignificanthandicap,andtoprovideprospectiveparentswithchoicesregardingcontinuationorotherwiseofthepregnancy.

Screeningcanreducetheriskofdevelopingaconditionoritscomplicationsbutitcannotofferaguaranteeofprotection.Inanyscreeningprogrammethereisaminimumoffalse-positiveresults(wronglyreportedashavingthecondition)andfalse-negativeresults(wronglyreportedasnothavingthecondition).TheUKNSCisincreasinglypresentingscreeningasriskreductiontoemphasizethispoint.

Screeningcanbeanemotiveissue.Whilescreeningforfetalproblemsisohenconsideredthemostemotionallychargedarea,itisimportanttorealizethatmaternalscreeningcanalsoraiseissuesandchallengesthatallhealthprofessionalsinvolvedintheserviceneedtobeequippedtohelpwith.ImaginetheemotionaljourneyamotherembarksonwhenfacedwithanewdiagnosisofHumanImmunodeficiencyVirus(HIV)inearlypregnancy.

Socialandpsychologicalimpactofscreeninginvestigations

Pregnancyisaprofoundandlife-changingevent.Duringthistimethemotherhastoadaptphysically, sociallyandpsychologicallyto the forthcomingbirthofher child.Manywomenfeelmoreemotionalthanusual(Raphael-Leff2005)andmayhaveheightenedlevelsofanxiety(Kleinveldetal2006;RaynorandEngland2010).AsGreenetal(2004)state,theincreasingavailabilityoffetalinvestigationshasbeenshowntocausewomenevengreateranxiety andstress.Anyfeelingsofexcitementandanticipationcanquicklychangewhenthemotherisintroducedtotheideathatsheis‘atrisk’ofhavingababywithaparticularproblem(Fisher2006).

Thereisevidencethatmothersnearingtheendoftheirreproductiveyears(witha

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higherrisk ofchromosomalabnormality)experiencepregnancyinawaythatisdifferenttoyoungerwomen.Oldermothersareohenmoreanxiousandhavefewerfeelingsofafachmenttothefetusat20weeksofpregnancy(BerrymanandWindridge1999).Psychologists,sociologistsandhealthprofessionalsnowgenerallyacceptthefindingthathigh-riskwomendelay afachmenttothefetusuntiltheyreceivereassuringtestresults.Rothman(1986)classicallytermedthisthe‘tentativepregnancy’,inastudyofwomenundergoingamniocentesis.

Anxietycausedbyconsiderationofpossiblefetal abnormalitymaybeaccompaniedbymoralor religiousdilemmas.Teststhatcandiagnosechromosomalorgeneticabnormalitiesalsocarry ariskofprocedure-inducedmiscarriage.Manyparentsagonizeaboutwhethertosubjectapotentiallynormalfetustothisriskinordertoobtainthisinformation.Parentsmaythenneedtoconsiderwhethertheywish toterminate orcontinuewithanaffectedpregnancy.Somereligiousauthoritiesonlysupportprenataltestingsolongastheintegrityofthemotherandfetusaremaintained.Therearealsoopposingviewsaboutthelegitimacyofterminatingapregnancy,evenwhenaseriousdisorderhasbeendiagnosed.Suchdilemmasareanunfortunatebutinevitablecostofthechoicesassociatedwithsomefetalinvestigations.

Despitethis,there areimportantadvantagestothe acquisitionofknowledgeaboutthefetusbeforebirth.First,societygreatlyvaluesthefreedomofindividualstochoose.Peopleareencouraged toacceptsomeresponsibilitywhenmaking decisionsabouttreatmentoptions,inpartnershipwithhealthcareprofessionals.Asecondadvantageisthatreproductiveautonomy maybeincreased.Womencanchooseforthemselveswhethertheywishtoembarkuponthelifelongcareofachildwithspecialneeds.Thismaybeviewedasempoweringandasameansofpreventinglatersufferingandhardshipforchildandfamilyalike.

Insummary,prenataltestingisatwo-edgedsword.Itenables midwivesanddoctorstogivepeoplechoicesthatwereunheardofinpreviousgenerationsandthatmaypreventmuchsuffering.However,insomecircumstancestheyactuallyincreasetheamountofanxietyandpsychologicaltraumaexperiencedinpregnancy.Thelong-termeffectsofsuchtraumaonfamilydynamicsarenotcurrentlyunderstood.

Howscreeningissetupandthemidwife'sroleandresponsibilities

Allmidwivesneedtohaveabroadunderstandingofscreeninginvestigationsbecausetheyareresponsibleforoffering,interpretingandcommunicatingtheresults.In theUK,theMidwives Rules andStandards (NMC2012)statethat midwives shouldworkinpartnershipwithwomentoprovidesafe,responsiveandcompassionatecare.Thisimpliesthatthemidwifeasakeypublichealthagentshouldenablewomentomakedecisionsabouttheircarebased onindividual needs.Somemidwivesspecializeindiscussingcomplextestingissueswithparentsandbecomeantenatalscreeningcoordinators.

InEnglandfrom1April2013,27ScreeningandImmunisationTeamswillhavethe

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responsibilityfor commissioningandoversightoftheUK NationalScreeningCommifee(NSC)AntenatalandNewbornScreeningprogrammes.TheUKNSChastheoverallresponsibilityfordeterminingtheseprogrammesand willensuretheQualityAssuranceaspectviaRegionalQualityAssuranceTeams.

TheUKNSC(2011a)recommendsthatdedicatedscreeningcoordinatorsoverseetherunningofscreeningprogrammesineveryTrust.Screeningcoordinatorsalsoprovidespecialistadvice andensure thatthere isaline ofreferralforwomenwhoseneedsare notmetbyroutineservices.Screeningfor pregnantwomenandnewbornbabiesisnowsuchacomplexprocessthattheroleofscreeningcoordinatorhasbecomeafull-timeroleinmostservices.

TheUKNSCpublishesanextremelyhelpful timelineforantenatalandnewbornscreeningthatwillhelpindividualstoseewhatisrequiredandbywhen(

Eachoftheindividualscreeningprogrammeshasanumberofkeyperformanceindicators(KPI)onwhichtheperformanceofindividualNationalHealthService(NHS)Trustsismeasured.ThemostrecentKPIdocumentrunsto45pages.Overseeingthedelivery oftheKPIsistheremitofthescreeningcoordinatorineachTrust,butitisthehardwork oftheprofessionalsonthegroundthatensurestargetsaremet.Asanexample,theKPIforscreeningforhepatitisBstatesthatatleast70%ofpregnantwomenwhoarehepatitisBpositiveshouldbereferredandseenbyanappropriatespecialistwithinaneffectivetimeframe(6weeksfromidentification).

TheKPIforscreeningforDownsyndromeat between10weeks+0daysand20weeks

+0 days states thatin97%ofwomentheremustbesufficientinformation forthewomantobeuniquelyidentified,andthewoman'scorrectdateofbirth,maternalweight,familyorigin, smokingstatusandultrasounddating assessmentinmillimetres, withassociatedgestationaldateandsonographerID,mustbeincludedontherequestform.

Failsafeproceduresarea necessarypartofthescreeningprocess.In theUKthesehavebeenimplementedtoensureallscreeningprocessesarecomplete.Thereareback-upmechanismsinadditiontousualcare,whichensuresifsomethinggoeswronginthescreeningpathway,processesareinplacefirstlytoidentifywhatisgoingwrongandsecondlytodeterminewhatactionshouldfollowtoensureasafeoutcome.

Allprofessionalsundertakingscreeningmustbeappropriately trainedandconfidentindiscussingtherisksandbenefitsofallscreeningprogrammes,andintheUKtheymustadheretotheNSCrecommendationsandstandards.

Documentation

Inwhateversystemispractised,gooddocumentationisvital.Themidwifeshoulddiscussandofferscreeningtests,recordthatthediscussionhastakenplace,thattheofferhasbeen made,thatthe offerhasbeeneitheracceptedordeclined.Itisveryhelpfulforthewholeteamengagedinantenatalcaretounderstandfromthedocumentationwhyscreeningisdeclined,ifthisisthecase.Womenfindbeingpersistentlyre-offeredascreening test that they have declined frustrating and annoying, and simply

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documentingthediscussionproperly,ratherthantickingaboxtoindicatethatscreeningwasdeclined,ishelpful.Thiscansometimesalsoleadontodiscussionthatcanrevealthata woman hasnotunderstoodthetest, thepurposeorthebenefits,whichcan help toimproveunderstanding.

Intheeventofdeclineforinfectiousdiseasesscreeningattheantenatal‘booking’appointment,aroutinere-offershouldbemadeatabout28weeks.Fromalitigationperspective,itisnotuncommonforwomenwhohavedeclinedscreeningbutexperiencedapooroutcometosuggestthattheywerenotofferedscreeningordidnotunderstandthe purpose ofthetestonoffer.Gooddocumentationandbeingabletoshowthatwritteninformationwasgiven canhelpinthecomprehensionofsuchcases.

Discussionofoptions

Whenofferingtests,itisnecessaryforthemidwife topresentanddiscuss the options,sothatwomencanmakeaninformedchoicethatbestsuitstheircircumstancesandpreferences.Midwivesarerequiredtodiscussoptionsfor testing ina mannerthatenablesshareddecision-making(Sullivan2005).This meansprovidingtheopportunitytodiscusschoiceswithatrained professionalwhoisimpartialandsupportive as thewomenmakedecisionsalongthescreeninganddiagnosticpathway.

There maybemixedfeelings about thefinaldecision.Sometimesitishelpfultoconsiderwhatthemother'sworst-casescenariowouldbe,asthatcanhelptodecidethebestwayforward.Theprinciplesforconsentforshareddecision-makingareshowninBox11.1.

Box 11.1

Principlesforobtaininginformedconsent

•Purposeoftheprocedure/test

•Allrisksandbenefitstobereasonablyexpected

•Detailsofallpossiblefuturetreatmentsthatcouldariseasaconsequenceoftesting

•Disclosureofallavailableoptions(thismayincludeteststhatareofferedbyprivateproviderswhererelevant)

•Theoptionofrefusinganytests

•Theoffertoansweranyqueries

Midwivescommonlyrecommendantenataltestssuchasinfectiousdiseasescreening,fullbloodcount orcardiotocographforreducedfetalmovements.However,testsforfetalanomalyrequireanon-directiveapproachthatenablesthemothertomakeaninformedchoice(Clarke 1994).Consent mustbeobtainedpriortoalltestsandthismust bedocumented.Standardizedprocessesallowsystemsto servewomen uniformlyandallowgoodqualityofcaretobeofferedtoall.IntheUK,theNSC(2011a)has published

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ConsentStandardsandGuidanceforthefetalanomalyscreeningprocesswhichcanbeusedasamodelinanyhealthcaresystem.

•Standard1:Allhospitaltrustsmusthaveacarepathwaytoprovide evidencethattheUKNationalScreeningCommittee(UKNSC)andNHSFetalAnomalyScreeningProgramme(FASP)informationbookletandleafletsarebeingused.

•Standard2:Allpregnantwomenmustbeoffered,at least24hoursbeforedecisionsaremade,up-to-dateinformationonfetalanomalyscreeningbasedonthecurrentavailableevidence.TheNHSFASPrecommendstheuseoftheUKNSC(2012)leafletentitledScreeningtestsforyouandyourbaby,availableonthe NHSFASPwebsite:

•Standard3:Alleligiblepregnantwomenmustbeoffered‘testing’andthisoffermustberecordedinthewoman'snotesand/orhospitalelectronicrecordsattheantenatal‘booking’appointment.

•Standard4:All decisions about thetestitselfmust berecordedinthewoman's hand-heldnotesand/orinthehospitalrecords.

It is important alldocumentation is datedandsignedbythe health professionalinvolved.

The UKNSC(2011a)guidanceisverycompleteanditisausefuldocumentforallmidwives toread.Keyaspects areshowninBox11.2.

Box 11.2

KeyaspectsoftheUKNSC(2011)guidanceonantenatal screening

•Thepregnantwomanmustunderstandtheconditionbeingscreenedfor.

•Themidwifeshouldexplainaboutthenature,purpose,risks,benefits,timing,limitationsandpotentialconsequencesofscreening.

•Thewomanshouldunderstandthatscreeningisoptional,andunderstandtherisksandbenefitsofnotundergoingscreening.

•IntheUKthereisthechoiceofcontinuingorterminatingapregnancyforseriousfetalabnormalities.

Localknowledgeshouldbeshared:how,whereandwhenthetestisdone:

•Whatthetestresultsmeanandpotentialsignificantclinicalandemotionalconsequences.

•Thedecisionsthatmightneedtobemadeat eachpointalongthe pathwayandtheirconsequences.

•Howandwhenthe results willbegiven.

•Howwomenprogressthroughthepathway,includingthosewhooptoutof

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screening.

•Thepossibilitythatscreeningcanprovideinformationaboutotherconditions.

•Thefactthatscreeningmaynotprovide adefinitivediagnosis.

•Whatfurthertestsmightbeneeded,e.g.chorionicvillussampling(CVS)andamniocentesis.

•Thatconfirmatory/repeattestingmayoccasionallyberequired.

•Balancedandaccurateinformationaboutthevariousconditionsbeingscreenedshouldbeprovided.

Assumptionsmustneverbemaderegardingknowledgeabouttheconditionsbeingscreenedfor.CommonmisunderstandingsarethatDownsyndromecannotoccurifithasnotpreviouslyoccurredinafamilyorthatawomanistooyoungtohaveanaffectedbaby.Manywomen(andtheirpartners)donotunderstandthatsyphilisisasexuallytransmifedinfection,butthattheinitialresultcanshowpositiveiftherehavebeensimilarnon-sexuallytransmittedinfections(suchasYaws).

WomenwhodeclinefirsttrimesterscreeningshouldknowthattheycantakeupsecondtrimesterscreeningforDown'ssyndromeif theychangetheirmindandthattheycanundergosecondtrimesterscreeningforfetalanomalyat18+0to20+6weeks.

Womenwhodeclineinitialscreeningforinfectionscanandshouldbeofferedscreeninglaterinthepregnancy.

Importantly,onlythewomanhastherightto consentto ordeclinethescreeningtests.Apartnerorfamilymemberhas norighttoconsentordecline on herbehalf.Women canwithdrawconsentfortestingatanytime.Thisdecisionshouldberecorded.

Theprocessofconsent

Consentisacomplexprocessnotasingleentity,andrequiresadequatetime.Itisimportanttoensurethatthewomanhashadthetimesheneedstoconsidertheinformationandcometoadecision.Thattherehasbeenenoughtimetoaskquestions,thatshefeels comfortableandhasinvolvedthoseshe wouldwish toin reachingadecision.Theextenttowhichwomenwanttoinvolveothers is veryvariable.

Theamountofinformationneededwillvarybetweenwomen.WomenwhodonotunderstandEnglish willrequireinterpretingservicesandotherservicesmight beneededforsomewomen.Notallwomenwillhavethecapacitytoconsent.Wherecapacity isindoubtthereareusuallylocalguidelinesastohowthisshouldprogressforwardthatarebeyondthescopeofthischapter.

Issuestoconsiderwhenpresentinginformation

Whendiscussingtests,itisimportanttounderstandthemotivationsandthoughtprocessesofpregnantwomen.Themotivationfortestingisohendifferentformotherandpractitioner.Forthefetalanomalyscreeningprogramme,theUKNSCrationalefor

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testingistoidentifyfetalanomalies;howevermotherscommonlyacceptthesetestsinordertogain reassurance that theirfetus isnormal(Huntetal2005).Mothersohenthinkthatfetalanomalytestssuchasultrasoundscansareanintegralormandatorypartoftheirantenatalcare.Theymayalsobeunawareofthereasons forperformingthetest andthiscancompoundtheshockoffindingproblemsorabnormalities(HealthTechnologyAssessment2000).

Whenwomenareanxiousorunderstress,theyarelessabletoremembertheinformationprovided(IngramandMalcarne1995).Parentsmayfeelvulnerableandlessabletoaskquestions.Thismayleadtodissatisfactionwiththequalityofcommunicationswithhealthcarers.Sinceanunbornfetusissomethingofanenigmatoparents,thismayincreaseanxietyandsensitivitytorealorimaginarycues.Forexample,professionalspractisingnon-directivecounsellingmaybeperceivedasevasiveandasconcealingbadnews.Oneparticularaspectofcounsellingthathasbeencriticizedbyparentsisthe portrayalofriskestimates(Al-Jaderetal2000).

Thereismuchevidencethatpeopledonotmakeconsistentdecisionsaboutundertakingtestsinpregnancyonthebasisoftheriskinformationreceived.Forinstance,amotherwithariskofDownsyndromeof1:150mayperceiveherselftobeataveryhighriskandmayrequestamniocentesis.However,othersmayviewthatsameriskasverylow.Thephenomenonofhowparentsinterpretriskinformationisnotfullyunderstood,althoughitisclearthatpersonalcircumstances,preferencesandbeliefsareanintegralpartofthisprocess.Forthisreason,itisvitalthat,withanyscreening,themidwifebeginsaconsultationbyinvestigatinghow muchthemotherknowsabouttheconditionbeingtestedfor,andwhatshealreadyknowsaboutthetestrisks, benefitsandtheconsequencesofresults.

Therearealsocommonbiasesinthewaypeopleinterpretriskinformation.Themidwifeshouldbeawareoftheseinordertohelpparentschoosethemostappropriatecourseofaction.Forexample,peopletendtoviewaneventasmorelikelyiftheycaneasilyimagineorrecallinstancesofit. Thismeansthata motherwhosefriendorneighbourhasababywithDownsyndromemaybesensitizedtothispossibilityandoverestimatethechancesofithappeningtoher.Motherswhoworkwithinfirmpeople,orthosewithadisability,aremostlikelytoseekprenataldiagnosis(Sjögren1996).Perhaps thesemothersareeasilyable toimagine the lifelongcommitmentofcaringfor achildwithspecialneeds.Thiscommonbiasinriskperceptionisimportantbecauseitmeansthatsomemothersmaynoteasilybereassuredbyreiterationofthefactthattheriskofaproblemmaybecomparativelyrare.

Explainingrisk

Thewayinwhichthemidwifetellsamotheraboutriskwillalsogreatlyinfluencehowthatriskisperceived.Forexample,amotherwhoistoldthatherriskofaparticularconditionis1in10maybemorealarmedthanifshehadbeeninformedthattherewasa90%chanceofnormality.or9outof10babieswillnotbeaffectedbythecondition.Thisisknownasthe‘framing’effect (KesslerandLevine1987).

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Peoplevaryconsiderablyinthewaysthattheyconsiderandunderstandrisk,soitisimportantthatthis informationispresentedin avarietyofwaysusingappropriatelanguage.The UKNSC(2011a)recommendtheuseoftheword‘chance’ratherthan‘risk’and thatthechanceoftheoutcome(whichforantenatalscreeningnowmainlyrelatestoscreeningforDown syndrome)begivenasapercentageaswellasaratio1 in x.Assuch,amidwifediscussinga1in100chanceofadisordershouldalsopointoutthefactthat99%or99outof100similarpeoplewillnotexperiencethatdisorder.Thismayhelppeoplecopewhenconsideringtestsorwhenanxiouslyawaitingresults.

Thereareother generalconsiderationsto takeinto accountwhen providinginformation(Hunter1994),asdelineatedinBox11.3.

Box 11.3

Generalprincipleswhenprovidinginformation

1.Be clear:explaineverythingintermsthatarenotmedicaljargonorcomplexterminology.

2.Beawarethat peoplecanrememberonlyalimitedamountofinformationat onetime–besimple,conciseandtothepoint.

3.Giveimportantinformationfirst.Thiswillthenberememberedbest.

4.Grouppiecesofinformationintologicalcategories,suchastreatment,prognosisandwaystocope.

5.Informationmayberecalledmoreeasilyifithasbeenpresentedinseveralforms.

Forexample,leafletscanbehelpful.

6.Offertoansweranyqueries.Givecontactnumbers,incasepeoplethinkofquestionsatalaterdate.

7.Donotmakeassumptionsaboutinformationrequirementsonthebasisofsocialclass,profession,ageorethnicgroup.

8.Summarize,checkunderstandingandrepeattheinformation.Askwhetherthereisanythingthatremainsunclear.

Source:Hunter1994

Ifatestisundertakeninpregnancy,itisgoodpracticetoensurethatthewomanisclearabouthow,whenandfromwhomshewillbeabletoobtaintheresult.Ifpossible,thereshouldbesomeoptionsavailable.

TheUKNSC(2011a)isclearthatthepersonorderingthetesthastheresponsibilitytoensurethatthetestisproperlycompletedandthatthewomanisinformedoftheresult.TheNationalInstituteforHealthandClinicalExcellence(NICE2008)antenatalcareguidelinesstatethateverywomanshouldhavetheresultsofalloftheirscreeningtestsrecordedintheirhand-heldnoteswithin14daysoratthe16weekantenatalappointment.Itthereforerequireseachmidwiferyteamtohaveaprocessforthemanagementoftrackingtestsperformedandtheresults,ameanstoinformwomen,a

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processoffail-safesothatwhen,aswillinevitablyhappen,atestisnotperformedorsamplenotprocessedbecauseinsomewaytheprocessfailed,thisisrecognizedinatimelyenoughfashionforthe testtoberepeated,andthat the resultsarerecordedinthewoman'shand-heldnotes.

Onalogisticalfront,thisisnomeantask.FailingsinthescreeningsystemareidentifiedasseriousincidentsandthereisaformalprocessintheUKthatmustbeundertakenwhenfailingsareidentified.Inpractice,themajorityofwomenwhofallbetweenstoolsarethosewhosepregnanciesdonotfollowtheroutineprocess,forinstancethosewhomoveorwhosepregnancydoesnotcontinue.Thesewomen,asmuchasanyoneelse,stillshouldbe informedofresultsthat areimportant tothem,suchas theresultsofinfectionscreening.

Individualscreeningtestconsiderations

Antenatalscreeningtestsare broadlydividedintothosethat are lookingforaprobleminthemotherthatcouldaffectthefetus,suchasaninfection,thepresenceofared-cellantibody,oraparticularhaemoglobinvariant,whichifpassedonbybothparentscouldcauseanissue,orthoselookingdirectlyforaprobleminthefetus.

Fetalscreeningtests

Populationscreeningofthefetus(i.e.thatofferedtoeveryone)isnowdirectedattwoareas:defining therisk ofababyhavingDownsyndrome(trisomy21),andthedetectionofspecificabnormalities.

ScreeningforDownsyndrome

Downsyndromeisthemostcommoncauseofseverelearningdifficultyinchildren.In theabsenceofantenatalscreening,around1in700birthswouldbeaffected(Kennardetal1995).WhilesomechildrenwithDownsyndromelearnliteracyskillsandleadsemi-independentlives,othersremaincompletelydependent.Aroundoneinthreeofthesebabiesarebornwithaseriousheartdefect.Theaveragelifeexpectancyisabout60years,althoughmostpeopledeveloppathologicalchangesinthebrain(associatedwithAlzheimer'sdisease)aftertheageof40(Kingston2002).

ScreeningforDownsyndromehasbeen drivenbybothhealtheconomicsandmaternalchoice.Thatisnottosay,however,thatallmotherswishtobescreened,orwouldacttoendapregnancyiftheyknewtheywerecarryinganaffectedfetus.Uptakeratesforscreeningvarydependingonthepopulationbeingscreened.Somemotherswillchosescreeningdespiteknowingthattheywouldnotactonaresultthatgavethemahighchance.Interestingly,thesinglelargestfactorindecidingwhethertotakefurthertestsaherahighchanceresultisthedegreeofmagnitudeofthechangeinrisk.Inotherwords,amotherwhohasa pre-testchance(basedonagealone)of1 in100 (1%), whohasascreeningresultof1in120(0.83%)willbelesslikelytowishtoproceedtofurther

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testingthanawomanwhohasapre-testchanceof 1in1000,whothen receivesaresultof1in120chance,eventhoughbothareatequalriskofgiving birthtoababy withDownsyndrome.

ThenationalscreeningprogrammeforDownsyndromeintheUKcomprisestheofferofoneoftwotests.Thegestationalagewindowforacombinedteststartsfrom10+0weeksto14+1weeksinpregnancy.

Thecombinedtestcomprisesmeasurementofthecrown–rumplength(CRL)(Fig.11.1)toestimatefetalgestationalage(datingscan),measurementofthenuchaltranslucency(NT)spaceatthebackofthefetalneck(Fig.11.2)andmaternalbloodtomeasuretheserummarkersofpregnancy-associatedplasmaproteinA(PAPP-A)andhumanchorionicgonadotrophinhormone(hCG).

FIG. 11.1Crown–rumplength.

FIG. 11.2Translucencymeasurement.

Usingthistest,90%offetusesaffected withDown syndromewould beexpected to fallintothehigh-chancecategory(achanceof1in150ormore)(thedetectionrate)with2%ofwomencarryingunaffectedbabieshavingachanceof1in150orhigher(ascreenpositiverateof2%).

Thequadrupletestwindowstartsfrom14+2weeksto20+0weeks.AmaternalbloodsampleisrequiredfortheanalysisofhCG,alpha-fetoprotein(aFP),unconjugatedoestriol(uE3)andinhibin-A.

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AsstatedintheUKNSC(2011b),ModelofBestPractice2011–2014,thistesthasalesserdetectionrateof75%andascreenpositiverateoflessthan3%,buthasbeenretainedbecausetherewillalwaysbewomenwhobooktoolateinpregnancyforcombinedtesting(about15%ofthepregnantpopulation)andwishtohavescreening.Womenpresentingaher20weeksareofferedultrasoundforabnormalityscreening,whichwill occasionallydetectan abnormalitythatincreasesthechancethatthebabyhasDownsyndrome,butthereisnopopulationscreeningavailableatthisgestation.

Womenneedtodecideas earlyintheirpregnancyaspossibleiftheywishtoundertakescreeningforDownsyndromeasearliertestingissuperior,andeaseofaccessisimportantinfacilitatingtesting.

Incounselling,women needtobeclear thatneitherscreeningtestgivesa guaranteeofnormality.Withcombinedscreening10%ofaffectedbabieswillbemissedandwithquadrupletesting25%ofDownbabieswillbemissed.Thisistermedthefalse-negativerate.

DiagnostictestingforDownsyndrome

IntheUK,womenwhoreceivearesultof1in150orhigherfromeitherfirstorsecondtrimester screeningorthosewomenwhohavepreviouslyhad achromosomalabnormalityorwho carryageneticdisorder willbeoffereddiagnostictesting,i.e.CVSoramniocentesis.TheNHSnolongerprovidesdiagnostictesting formaternalagealoneorfollowingalowchancescreeningtestresult,althoughprivatelyavailableservicesareusuallyeasytoaccess.

CVScanbeperformedfrom11weeksofpregnancy.Usuallytheprocedureiscarriedouttransabdominally(Fig.11.3),thoughoccasionallyatranscervical(TC)routeisneeded.Themiscarriagerateisohenquotedas2–3% butinmostfetalmedicineunitstheprocedure-relatedlossrateiscloserto1%(thoughTCsamplingrisksarehigher).Aprovisionalresultisusuallyissuedonadirectpreparationat1–2days.Ifthisresultshowsnoevidenceofanextrachromosome21itcanbetakenas99.9%certainthatthefetusdoesnothavetrisomy21.However,asconfinedplacentalmosaicismcanrarelyoccur,whichgivesafalse-negativeresult,atthisstagedefiniteconfirmationcannotbemadeuntilthecultureresultis availableat14–21days.

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FIG. 11.3TransabdominalCVS.

Amniocentesiscanbeperformedaher15weeks(Fig.11.4).Theprocedure-relatedlossrateisusuallyno higherthan1%andinmanyunitsiscloserto0.5%. Rapidtestingusingpolymerasechainreactionorfluorescentinsituhybridizationcanusuallymeanthataresult fortrisomy21(andusually13and18)is availablein2–3workingdays.

FIG. 11.4Amniocentesis.

AdiagnosisofDownsyndromecanbeaccuratelymadeusingCVSoramniocentesis,butitcannotgivecertaintyastotheseverityofthedisorderorthequalityoflifeofaparticularindividual.Responsestoadiagnosiswillvary,accordingtocultural,social,

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moralandreligiousbeliefs.

Screeningforhaemoglobinopathies

TheNHSNSCantenatalandnewbornscreeningprogrammesincludeantenatalscreeningforfetalhaemoglobinopathies.Thisshouldbelinkedwiththenewbornbloodspotscreeningprogramme,whichtestsforsicklecelldisease.Linkingresultsofparentsandbabiesincreaseshealthprofessionalsaccesstofamilieswithgeneticdisorders,allowingtheresultstobeavailablethroughouttheindividual'slife,reducingrepeatscreening.Haemoglobinopathiesareinheriteddisordersofhaemoglobinandaremoreprevalentincertain racialgroups.Antenatalscreeningidentifiesabout22,000 carriersofsicklecelldiseaseandthalassaemia intheUKeveryyear(NHSSickleCellandThalassaemiaProgramme2011).

Currently,intheUK,antenatalscreeningforhaemoglobinopathyisbasedonpopulationprevalence.Highprevalenceareashaveuniversalscreening(offerallpregnantwomenelectrophoresisscreeningforhaemoglobinvariantsandthalassaemiatrait).Lowprevalence areas use thenationalFamilyOriginQuestionnaire(FOQ)todeterminegeneticancestryforthelasttwogenerations(ormoreifpossible).AllareascollectinformationontheFOQintheirmaternitypopulation.Thisinformationis neededbylaboratoriestohelpinterpretscreeningresults.

Inlow-prevalenceareas,womenwithgeneticancestrythatincludeshigh-riskracialgroupsareofferedelectrophoresistesting.Ifthemotherisfoundtobeahaemoglobinopathycarrier,partnertestingisthenrecommendedand shouldbeofferedsoonahertheresultisavailable.Geneticancestryisalsoimportantwheninterpretingscreeningresults.Itisimportanttoestablishmaternalironlevelswhencarrier statusforthalassaemiaissuspected,sinceirondeficiencycangiverisetosimilarredcellappearances.(e.g.alphathalassaemia).Mosthaemoglobinopathiesarerecessivelyinherited,sothefetuswouldhavea1in4chanceofinheritingthedisorderanda1in2chanceofbeingacarrier.

Pre-testinformationforantenatalhaemoglobinopathyscreening

•Inearlypregnancy,informationshouldbesupplied.IntheUKthismeansthatallwomenshouldreceivetheNSC(2012)informationbookletScreeningtestsforyouandyourbabyasearlyinpregnancyaspossible.

•Theinformationshouldbeprovidedinanappropriatelanguageorformat.

•Testingshouldbeperformedasearlyinpregnancyaspossible,ideallyat8–10weeks'gestation,asscreeningdecisionsareoftengestation-dependent.

•Womenwhobooklateinpregnancyshouldbeofferedhaemoglobinopathyscreeninginthesamewayatthefirst point ofcontact.Optionsforendinganaffectedpregnancymaybelimited.

Wherebothparentsareidentifiedascarriers, theyneedurgentcounselling.In theUKparents are referred urgentlyto the PEGASUS (Professional Education for Genetic

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AssessmentandScreening)trainedmidwifeforspecialistcounsellingortothecombinedobstetric/haematologyclinicatthebookinghospital.Diagnostictestingby CVSoramniocentesisshouldbeoffered.

Wherepaternityisunknown,thefatherofthebabyisunavailableordeclinestesting,thewomanshouldbeofferedacounsellingappointmenttocalculatethepossibilityofthebabyhavinganinheritedhaemoglobindisorderandanofferofdiagnostictestingmadeiftheriskswarrantthis. Allwomenwillbeofferedneonatalbloodspotscreeningat5days,whichwilldetectsicklecelldisease(butnototherhaemoglobinopathies).

Ultrasonographyforfetalscreening

In theUK,theNSC(2011a)standardsarethatallpregnantwomenshouldbeofferedtworoutineultrasoundscans.Theseincludeanearlypregnancyscan(usuallytimedtobeabletoperformtheNTmeasurementifrequested)andan18–20weekfetalanomalyscreeningscan.Ultrasoundworksbytransmifingsoundataveryhighfrequency,viaaprobe,inanarrowbeam. Whenthesound wavesenterthebodyand encounterastructure,someofthatsoundisreflectedback.Theamountofsoundreflectedvariesaccordingtothetypeof tissueencountered;forexample,fluiddoes not reflect soundandappearsasablackimage.Conversely,bonereflectsaconsiderableamountofsoundandappearsaswhiteorechogenic.Manystructuresappearasdifferentshadesofgrey.Generally,picturesaretransmifedin‘realtime’,whichenablesfetalmovementstobeseen.

Safetyaspectsofultrasound

Ultrasoundhasbeenusedasadiagnosticimagingtoolsincethe1950s,sowearenowintothethirdgenerationofscannedbabies.Itseemsreasonabletoassumethatanymajoradverseeffectsofthistechnologywouldhavebecomeapparent beforenow.However,modernmachineshavehigherresolutionsandindicationsforultrasoundscanninghavegreatlyincreased.Thismeansthatlevelsofexposuretoultrasoundhaveincreasedinpregnancy.Althoughthetechnologyisconsideredsafe,itshouldbeusedwithrespectandonlywhenthereisgoodindication,andcareshouldbetakentolimit exposuretimeandthethermalindicesshouldbecontrolled(EuropeanCommifeeofMedicalUltrasoundSafety2008).Ultrasoundisadiagnostictool,butdiagnosiscanonlybeasreliableastheexpertiseoftheoperatorandthequalityofthemachine.AsWood(2000)states,abnormalitiesmaybemissedorincorrectlydiagnosediftheoperatorisinexperiencedorinadequatelytrained.

Women'sexperiencesofultrasound

Ingeneral,womenexperienceultrasoundasapleasurableopportunitytohavevisualaccesstotheirunbornbaby(Sandelowski1994).Indeed,ultrasoundscanshavebeenshowntoincreasepsychologicalafachmenttothefetus(Sedgmanetal2006).Parentshaveaprofoundcuriosityabouttheir babyandascancanturnsomethingnebulousintosomethingthatseemsmuchmorerealasalivingindividual(Furness1990).Thiscanbe

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particularlyimportantforawoman'spartnerandfamily, whodonothavetheimmediatephysicalexperienceofthepregnancy.Womentendtoregardtheirscanasprovidingageneralviewoffetalwell-being:thefactthatthefetusisalive,growinganddeveloping.However,thisreassuranceistemporaryandbeginstowearoffaherafewweeks(Clementetal1998).Mothersmaythenseekotherformsofreassurance(e.g.monitoringfetalmovements,auscultationofthefetalheartbeat).Thisinitialreassurancemayalsocreateanenthusiasmforscanswhenthereisnoclinicalindication.

Scansmayalsocauseconsiderableanxiety,however,particularlyifthereisasuspectedoractualproblemwiththefetus.Thereisevidencetosuggestthatwomenwhomiscarryahervisualizationofthefetusonscanmayfeelaheightenedsenseofanguishbecausethefetusseemedmorereal.Thismayalsobethecaseforparentsconsideringterminationof pregnancyonthegroundsoffetalabnormality.However,others mayviewtheirscanas atreasuredmemoryofthebabytheylost(Black1992).

Theidentificationoffetalabnormalityintheantenatalperiodhasdifferingpsychologicaleffectsforparentswhenthepregnancyistocontinue.Someparentshavereportedfeelinggratefulthattheywereabletoprepareforthebirthofachildwithadisability(Chifyetal1996).However,othershavereportedfeelingsofwishingtheyhadnotknownabouttheirchild'sproblemsbeforebirthbecausethiscreatedapowerfulimageofthefetusasa‘monster’.Someparentsreportedthistobefarworsethantherealityofcaringforthebabyaherbirth(Turner1994).Itisnecessaryformidwivestobemindful ofthepowerfulpsychologicaleffectsultrasoundscans haveonpregnantwomenandtheirfamilies,ifsensitiveandappropriatecareistobegivenatthispotentiallydistressingtime.

Themidwife'sroleconcerningultrasoundscans

Asforallprocedures,mothersshouldbefullyinformedaboutthepurposeofthescan.Informationshouldbegivenaboutwhichconditionsarebeingcheckedforandwhichproblemsthescanwouldbeunabletodetect.Becauseofthepleasurableaspectofseeingthefetus,ultrasoundscanshavetraditionallybeenteststhatmothersundertakewillingly,withoutpriordiscussionandconsiderationofpotential consequences.Ultrasoundscreeningforfetalabnormalityisascreeningtest andassuchwomenshouldbecounselledastothepurpose,choicesand pitfallsofscreening sothattheycandecidewhetherornottheywishtoundergoaprocedurethatmaybringunwelcomenews.Womenshouldbe awarethatultrasoundscansareoptionalandnotaninevitablepartoftheircare.

Womenshouldalsounderstandthatanormal‘scan’doesnotguaranteenormality inthebaby.Box11.4showsthedetectionratesforthecommonlyassessedabnormalities,whichshouldbesharedwithwomen.

Box 11.4

Detectionratesforcommonlyassessedfetalabnormalities

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Anencephaly / 98%
Openspinabifida / 90%
Cleftlip / 75%
Diaphragmatic hernia / 60%
Gastroschisis / 98%
Exomphalos / 80%
Seriouscardiacabnormalities / 50%
Bilateralrenalagenesis / 84%
Lethalskeletaldysplasia / 60%
Edwards'syndrome(trisomy18) / 95%
Patau'ssyndrome(trisomy13) / 95%
Source:UKNSC2010NHSFetalAnomalyScreeningProgramme:18+0 to20+6 WeeksFetalAnomalyScanNationalStandardsandGuidanceforEngland:Appendix9

Thereisevidencethat,althoughsomemothersmayfindthisinformationdisturbing,mostfeelthatthisisoutweighedbythepositiveaspectsofseeingthebabyandgainingreassurance(Oliveretal1996).Indeed,extrainformationaboutthepurposeofthescanhasbeenshowntoincreasewomen'sunderstandingandsatisfactionwiththeamountofinformationreceived,whiletheproportionofwomenacceptingascan(99%)appearstoremainunchanged(Thorntonetal1995).

TheRoyalCollegeofObstetriciansandGynaecologists(RCOG2000)recommendsthat,whereverscansareperformed,amidwifeorcounsellorwithaparticularinterestorexpertiseintheareashouldbeavailabletodiscussdifficultnews.Allwomenwithasuspectedorconfirmedfetalanomalyshouldbeseenbyanobstetricultrasoundspecialistwithinthreeworkingdaysofthereferralbeing madeorseenbyafetalmedicineunitwithinfiveworkingdaysofthereferralbeingmade(NSC2011a:Standard4).Effectivemultidisciplinaryteamworkingandcommunicationarethereforeessential.Itisalsogoodpracticeforthemidwifetoliaisewiththeprimaryhealthcareteam,whowouldnormallycarryoutthemajorityofantenatalcare.Withtheincreasinguseofclient-heldrecords,mothersmayhavemoreopportunitytoscrutinizethewrifenresultsoftheir scan.Midwivesmayincreasinglybecalledupontoexplainand discussthesefindings,bothinhospitalandinthecommunitysetting.

Firsttrimesterpregnancyscans

Allwomenshouldbeofferedafirsttrimesterscan.Thepurposeofthisistoestablish:

•thatthepregnancyisviableandintrauterine(notectopic);

•tomeasuretheNTifthegestationisappropriateandscreeningforDownsyndrome isaccepted;

•toaccuratelydefinethegestationalage;

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•todeterminefetalnumber(andchorionicityoramnionicityinmultiplepregnancies);

•todetectgrossfetalabnormalities,suchasanencephaly(absenceofthecranialvault).

Earlyultrasoundscanningisbeneficial,inreducingtheneedtoinducelabourforpost-maturity(Whitworthetal2010).A gestationsaccanusuallybevisualizedfrom5weeks'gestationandasmallembryofrom6weeks.Until13weeks,gestationalagecanbeaccuratelyassessedbyCRLmeasurement(thelengthofthefetusfromthetopoftheheadtotheendofthesacrum).Caremustbetakentoensurethatthefetusisnotflexedatthetimeofmeasurement.Mothersareaskedtoafendwithafullbladder,sincethisaidsvisualizationoftheuterusatanearlygestation.

Dealingwithincreasednuchaltranslucency

A nuchaltranslucencyof>3.5mmoccursinabout1%ofpregnancies(seeFig.11.2).ItisconsideredtobethethresholddefinitionofanincreasedNTabovewhichtheriskofother(non-chromosomal) abnormalitiesincreases.IncreasedNTisassociatedwithariskofchromosomalabnormalitiesandalsowithotherstructural(mainlycardiac)abnormalities(>10%risk),geneticsyndromesandanincreasedfetallossrate.WhereanincreasedNTisseenregardlessofwhetherscreeningforDownsyndromewasdeclined,thepotentialfor problemsto bepresentmustbediscussedandideallyreferraltospecialistscanningandcounsellingarranged.Inthepresenceofanormalkaryotype,ifnostructuralabnormalitiesarefoundtheUKNSC(2011a)statesthattheincidenceofadverseoutcomeisnotincreased,butalsoacknowledgesthatthechanceofdevelopmentaldelayis2–4%.

Wherediagnostictestingand18–20weeksultrasoundisnormalitisreasonabletobeoptimisticregardingoutcome,butitisworthrecognizingthatparentswillcarrytheanxietyofuncertaintywith themthroughand evenbeyondtheendofthepregnancyandwilloftenrequire alot ofsupport.

Secondtrimesterultrasoundscans

Aher13+6 weeksofpregnancy,gestationalageisprimarilyassessedusingtheheadcircumference(HC).

Thedetailedfetalanomalyscreeningscan

Thisscanisusuallyperformedat18–20+6weeksofpregnancy.Thepurposeofthisscan istoreassurethemotherthatthefetushasnoobviousstructuralanomaliesthatfallintothefollowingcategories:

•anomaliesthatareincompatiblewithlife;

•anomaliesthatareassociatedwithsignificantmorbidityandlong-termdisability;

•anomaliesthatmaybenefitfromintrauterinetherapy;

•anomaliesthatmayrequirepostnataltreatmentorinvestigation.

Detectionratesshouldbeinlinewiththoseoutlinedearlier.Technicaldifficulties,suchasfetalposition, multiplepregnancy,fibroidsormaternalobesitymaymeanthata

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secondscanbefore23weeksisoffered.Somestructuralproblemsdonothavesonographicsignsthatwouldbevisibleatthisgestationorevenatall.Analatresiadoesnothaveaclearappearanceonultrasound;hydrocephalusandotherbowelobstructionsmaynotappearuntillaterinpregnancy.Diagnosismaythereforenotbepossible.TheUK NSChasdefinedwhichstructuresshouldbeexamined(Box11.5)andwhichimagesshouldbestoredas part ofthewoman's record.

Box 11.5

18+0 to20+6 weeksfetalanomalyultrasoundscanbasemenu

•Spine,vertebraeandskincoveringintransverseandlongitudinalsections.

•Headandneck:Headshapeandinternalstructures(cavumpellucidum,cerebellum,ventricularsizeatatrium).Nuchalfold.Faceandlips.

•Thorax:Four-chamberviewofheart,cardiacoutflowtracts,lungs.

•Abdominalshapeandcontent –at levelofthestomachwithsmallportionofintrahepaticvein,abdominalwall,renalpelves,bladder.

•Limbs:Arms –threebonesandhand(metacarpals).Legs–threebonesandfoot(metatarsals).

•Placentallocationandamnioticfluid.

Source:UKNSC2010NHSFetalAnomalyScreeningProgramme:18+0 to20+6 WeeksFetalAnomalyScanNationalStandardsandGuidanceforEngland:Appendix1

SomefeaturesonultrasoundmaybeseenthatincreasetheriskofanotherproblemsuchasDownsyndrome.Anincreasedskinfoldmeasurementof>6mmatthelevelofthenuchalfold(a differententityto thenuchaltranslucency)shouldbe notedasthereisanassociatedincreaseintheriskforDownsyndromeofatleast10-fold.Mildcerebralventriculomegalyshouldbenotedasthereisagainanincreasedriskofchromosomalabnormalitiesofabout10%.Echogenicbowelcanbeseenincasesofcysticfibrosis,fetalinfection,and ifassociated with growth restriction and mild renal pelvis dilatation(>7mm)canprogresstosignificanthydronephrosis.

Whatusedtobetermed‘sohmarkers’are nolongerconsideredtohaveanysignificantimpactontheriskofchromosomalabnormalityinisolationorcombination,andaretermed‘normalvariants’andarethereforenotusuallyreported(choroidplexuscysts,two-vesselcord,dilatedcisternamagna,echogeniccardiacfocus).

Advantagesanddisadvantagesof fetalanomalyscans

Providedthesonographerhassufficientexpertise,manylethalorseverelydisablingconditionscanbedetectedduringthe18–20weekscan.Thereisalsoanincreaseinfirsttrimesterdiagnosis.Althoughthismeansthatparentsmaybefacedwithdifficultandunexpecteddecisions,itallowsparentsthechoicesthatwouldbedeniedwithoutthis

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knowledge.Furthermore,manyparentsareofferedreassurancethatnoobviousabnormalitieswereseen.Forneonatesrequiringearlysurgicalorpaediatricinterventions,priorknowledgeoftheabnormalityallowsaplanofcaretobeevolvedinadvanceofthebirth.Themothercanthengivebirthinaunitwithappropriatefacilities.Thishasbeenshowntoreducemorbidityincasesofgastroschisis(anabdominalwalldefect,adjacenttotheumbilicus,allowingtheintestinesandotherabdominalorgansto protrudeoutsidethebody),cardiacabnormalitiesandintestinalobstruction(Romeroetal1989).Forparentswhochooseto continuethepregnancyknowingthatthebabyhasalife-limitingcondition,carefulplanningregardingplaceofbirth,careofthebabyaherbirthandmultidisciplinarysupportcanbeprovided.

Insummary,the18–20weekscanappearstoconferpsychologicalandhealthimprovementbenefitsinsomecases,butalsohasthecapacitytocausegreatanxietyanddistress.Caremustbetakentoensurethatparentsarefullyinformedofthepurpose,benefitsandlimitationsofultrasoundscansbeforetheyconsenttothisprocedure.

Newandemergingtechnologies

Fetalimagingtechniques

Ultrasoundscansinpregnancy havebeendiscussedatlengthinthischapter,sincetheyareimportantfetalinvestigations.Womengenerallyseetwo-dimensional(2-D)images oftheirunbornbaby.However,there isa growingmarketforthree-dimensionalultrasoundimaging (3-D).Assuch,multipleimagesarestoreddigitallyandthenshadedto producelife-likepictures.Thistechniquecanassistthediagnosisofsurfacestructuralanomalies,suchasclehlipandspinabifida,andimprovementsarebeingseenincardiacandneurologicalscanning(Sandelowski1994;Sedgmanetal2006).

Magneticresonanceimaging(MRI)hasalsobeenappliedintheexaminationofthefetusoverthelasttwodecades.Thistechniquehasnotbeenwidelyappliedbecauseultrasoundcangivesimilardiagnosticinformationatalowercost.However,MRIhasacontributiontomake,particularlywhenexaminingthebrain.Thereisevidencethatthismayprovideadditionalinformationandchangethecounsellingandmanagementfora significantnumberofpregnancieswherebrainabnormalitiesaresuspected(GlennandBarkovich2006).AfurtherapplicationisthatMRIoffersanalternativetopostmortemfollowingterminationorperinataldeath.Thiscanofferinformationtoparentswhodeclinepostmortembecauseofitsinvasivenature(BrookesandHall-Craggs1997).MRIimaginghasbeenusedtorefinethediagnosisofmanyotherconditionsincludingdiaphragmaticherniasandsacrococcygealteratomas(KumarandO'Brien2004).

FreefetalDNA

MuchworkisnowbeingdoneonthetechnologythatidentifiesfreefetalDNAinthematernalcirculation.Alreadyitispossibletoidentifywithgreat(thoughnot100%)accuracy,fetalsex,bloodgroupandsome geneticdisorders. Before long RAPID(ReliableAccuratePrenatalnon-InvasiveDiagnosis)studywillreporttheresultsoftheresearch

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intotestingforDownsyndromeusingthistechnology.AlreadyatestisavailableprivatelyintheUnitedStates.Thiswillundoubtedlyincreasethetrue-positiverateanddecreasethefalse-negativerateforscreeningforDownsyndrome,whichwillbecomeavailableasabloodtest.Confirmatorytestingwillstillberequired,butfewertestswillbeneeded.FreefetalDNAisnowroutinelyusedtodeterminefetalbloodgroup(seebelow).

Screeningformaternalconditions

Therationaleforscreeningamotheristodetectconditionsthatareamenabletotreatmentandwillhavepotentialhealthbenefitsforherandherbaby.Inthemain,inpregnancy,screeningisfocusedonthosethatcarryimprovedoutcomesforthebaby.

Infectiousdiseases

IntheUKtheNSCprogrammeforscreeningofinfectiousdiseasesinpregnancyrecommendsthatallpregnantwomenarescreenedfor:

•HIV

•syphilis

•hepatitisB(HBV)

•rubella.

Theinfectiousdiseasesscreenedformeetthescreeningcriteriainthattheyareimportantandinterventioncanreduceharm.Rubella screeningcannotreducetheriskifamotherdevelopstheillnessbutallowsimmunizationinthefuturetoreducerisk.

Humanimmunedeficiencyvirus(HIV)

KnowledgeandadequatemanagementofwomenwithHIVcanreducemothertochildtransfertolessthan1%andimprovematernalhealth.Screeningshouldbeofferedatbookingandagain laterin pregnancyinwomen athigh risk(e.g.women whoarepaidforsex,womenwhohaveanuntestedpartnerfromanareaofhighprevalence,intravenousdrugusers).Womenwhodeclinescreeningshouldalsobere-offeredtestinglaterinpregnancy.

HepatitisB(HB)

AdequateimmunizationprogrammesforinfantsatriskofverticaltransmissionofHBVcanreduceinfantinfectionratesby90%andimprovementsinmaternalhealthcanbemade.

ReferraltoaspecialistisrequiredforwomenwhoarefoundtobehepatitisBpositive.Establishingtheneonatalandmaternalriskwillbedeterminedbytestingofantibodyandantigenstatusandviral DNAlevels.OccasionallyhepatitisBcanreactivateinpregnancyandknowledgeofstatuscanaidmanagementofthepregnantmother.

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Syphilis

SyphilisusedtobearareinfectionintheUK,buttheincidenceisnowinexorablyrising.Treatmentofsyphiliscanpreventpregnancylosspluscongenitalsyphilis,andpreventlong-termproblemsforthemother.Apositivescreeningresultdoesnotdistinguishbetweensyphilisandothertreponemalinfections,sospecialistinputisrequirediftheinitialscreeningtestispositive.

Inallthree oftheaboveinfections,knowledge of infectioncan preventunwifinginfectionofsexualpartners.

Rubella

Screeningforsusceptibilitytorubellaaimstoidentifythe3%ofwomenwhoaresusceptible,tocounselaboutavoidanceofpotentiallyinfectedindividualsduringpregnancyandtoofferpostnatalvaccination.

Fortheaboveinfections,testinginearlypregnancyisrecommended.Wrifeninformationshouldbeprovided atleast24 hourspriortodecisionsbeingmade. Inorderforthewomantomakeaninformedchoice,themidwifeshoulddiscussthefollowingpoints:

•Theinfectionsthatarescreenedfor,theirroutesoftransmissionandtheimplicationsofapositive test.

•Thebenefits,tobothmotherandbaby,tobegainedfromtheidentificationandmanagementofthosewithpositiveresults.

•Theresultsprocedure,includingthefeedbackofresultsandthepossibilityofafalse-negativeorfalse-positiveresult.

•Allpregnantwomenshouldbeadvisedthatiftheydevelop,orareexposedto,arashduringthepregnancytheyshouldseekprofessionaladvice.

Thattheofferwasmadeandtheresponsetotheoffershould bedocumented withthedate.Women whoinitiallydecline shouldbe re-offeredtestingatalaterdate;usuallyit isbesttodothisbefore28weeks.Iftestingisdeclineditisgoodpracticetoenquirewhyand toexploreanddocumentthereasons.Womenwhobooklateorwhoarriveuntestedinlabourcanbeurgentlyscreened.

Womenwithapositiveresultforsyphilis,HIV orHBV shouldbeseenandcounselledassoonaspossibleandwithin10daysintheUK.Appropriatereferralsshouldthenbemadetoensurethat thecorrect carepathwayisinducted.

Screeningforinfectiousdiseasesinpregnancycanbeenormouslychallengingforthemotherandforthemidwife.TheculturalandsocialstigmathatisstillafachedtoadiagnosisofHIVmeansthatsomewomenwillbereluctanttoconsidertestingor maybedevastatedwhenapositivetestisconfirmed.Issuessuchaspartnertestingneedsensitiveexplorationandshouldbeundertakenbythewidermultidisciplinaryteamthatwillcareforthesewomen.Themidwifeneedstohaveenoughknowledgetounderstandthedisease,theprocessfollowingapositivetestandtheabilitytoanswerquestionsordirectwomentotheanswers.

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Newscreening

IntheUKscreeningdoesnotexistonapopulationbasisyetforGroupBStreptococcus(GBS).GBSiscarriedinthe genitaltractandgutofmanyhealthypeople(between10and40%).Itisestimatedthatabout25%ofpregnantwomenintheUKcarryGBS. IntheUKGBSiseitherdetectedopportunisticallyorbyscreeningforhigh-risksituations,suchasaherprematureorprolongedruptureofthemembranes.Usingthisstrategy0.5/1000babiesareaffectedbyearlyonsetGBSdisease,adiseasethatcancausesevereproblemsforthesebabies,includingmeningitis anddeath.Newwork onwhyonlysomebabiesareaffected hasfocusedontheabilityofthemothertopassonGBSantibodies,butthishasnotbeenabletoidentifyaveryhigh-riskgroupthatcouldbeeffectivelytargeted.

IntheUnitedStatesscreeningisofferedbyvaginalswabsat35–37weeks.However,theriskofGBSintheUnitedStatesisconsiderablyhigher,againforreasonsthatarenotentirelyunderstood.

TheNSC(UK)isconsultingonwhethertoincludeGBSscreeningwithintheprogrammeforthefuture.Importantconsiderationsaretheeffectofantibioticsonasmanyas25%ofthepregnantpopulation,weighedagainsttheharmtoabout340babiesperyear.

Mid-streamurinetesting

Screeningforasymptomaticbacteriuriaisrecommendedasinpregnancyprogressiontopyelonephritiscanoccurinupto25%ofwomen.Pyelonephritiscanbelife-threateningandcanleadtomiscarriageandprematurelabour.Treatmentissimpleandeffectivewithappropriatelytargetedantibiotics.

Screeningforanaemia

Anaemiaisoneofthecommonestcomplicationsofpregnancy.Themostcommonreasonforirondeficiencyanaemiainpregnancyistheincreaseddemandsofthefetusforiron.Riskfactorsforthedevelopmentofirondeficiencyinpregnancyincludeirondeficiencypriortopregnancy,hyperemesis,vegetarianorvegandiet,multiplepregnancies,pregnancyrecurringafterashortintervalandbloodloss.

Pregnantwomenshouldbeofferedscreeningfor anaemia inearlyinpregnancyandat28weeks.Thisallowsenoughtimefortreatmentifanaemiaisdetected.

HaemoglobinlevelsoutsidethenormalUKrangefor pregnancy(thatis,11 g/dlatfirstcontactand10.5g/dlat28weeks)shouldbeinvestigated.Providedtherearenounusualfeatures tosuggest anothercausefortheanaemia,treatmentwith iron can bestartedandabloodtestforserumferritinsentatthesametimetoconfirmironstoresarelow.Thewomanshouldbeaskedifsheisknowntohaveahaemoglobinopathy.ThesewomenshouldbedirectlyreferredtoanObstetricHaematologyclinicforassessment.

Screeningforredcellantibodies

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AllpregnantwomenshouldbeofferedantenataltestingtoassessABOandrhesusstatusandtolookforredcellantibodies.Therewillusuallyberelevantnationalguidelines,whichwillspecifytheintervalsatwhichthisshouldtakeplace.Thiswillvarydependingonthewoman'sRhesus(Rh) typeandwhetheranyredcellantibodiesaredetected.

Redcellantibodiesareantibodiesagainstredcellantigens,andthe relevancetopregnancywillvarydependingonthetypeandlevelofthecirculatingantibody.Someantibodiesoccurnaturally,withoutanysensitisingevent,butmostoftheimportantonesrequireasensitisingeventsuchasapreviouspregnancyortransfusion.AntibodiestotheABOsystemtendtobenaturallyoccurring,asdoesanti-E.

Onceanantibodyhasbeenidentifieditwillberelevanttounderstandtheissuesforboththemotherandbaby.

Forthemotherwithanyred-cellantibodythemajorissueisrelatedtoincreaseddifficultyincrossmatchingblood.Womenwithantibodieswillnotbeabletoundergorapidelectroniccrossmatchingandthereforeforwomenatany increasedriskinlabourofhaemorrhage,crossmatchingintheearlystagesor beforeplannedbirth maybeprudent.

Forthefetus,red-cellantibodiesareofsignificanceasIgGantibodiescancrosstheplacenta.Ifthefetalredbloodcellscarrytheantigentheantibodyisdirectedagainsttheywillbedestroyed.Thiscanleadtofetalanaemiaandinseverecasescausefetalhydrops.Jaundiceandkernicterus(braindamagecausedbyveryhighunconjugatedbilirubinlevels)intheneonatalperiodarethemajorneonatalrisks.

Routineantibodytestinginpregnancyaimsto:

•identifyRhesus-negativewomenwhowillbeeligibleforanti-Dimmunoglobulinprophylaxis

•identifywomenwhoaredifficulttocrossmatchsothatsteps canbetakentominimizerisk

•identifywomenwithantibodies that put thefetus at riskofhaemolytic diseaseofthenewborn(HDN).

TheUKrecommendsthatallwomenshouldbetestedatbookingandagainat28weeks'gestation(NICE2008).

TherearemanyredcellantibodiesanditisusefultounderstandwhichonesareimportantcausesofHDN.

•AntibodiestotheRhesusantigensarethemostcommontocauseproblems.

•RhesusDantibodiesaretheprinciplecauseofsevereHDN.

•RhesusccancauseHDN,especiallyifantibodiestoRhesus Earealsopresent

•RarelyantibodiestoRhesusE,e,CandCWcancauseHDN.

Antibodiestonon-RhesusantigenscanalsocauseHND.Anti-K(Kell)antibodiesareanimportantcauseofsevereHDN.Theseantibodiesnotonlydestroythefetalredcells,butinhibitproductioninthebonemarrow,exacerbatinganydevelopinganaemia.

OtherantibodiesknowntocauseHDNlesscommonlyincludeantiFya(Duffy),antiJka(Kidd)andantiS.

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AntibodiestotheABOsystemmaybedetectedonroutinetesting.Ingeneraltheseoccurin GroupOwomen andarenaturallyoccurringanti-Aandanti-Bantibodies.BecausetheseantibodiesareIgMantibodiestheydonotcrosstheplacentaanddonotharmthefetus.OccasionallysomegroupOwomenproduceIgGantibodieswhencarryinggroupAorBinfants.TheseIgGantibodiescancrosstheplacentaandcauseHDN,butthistendstobemild.

Howtheresultsarepresented

Antibodylevelsareeithergivenastheactualmeasuredamountorasthedilutionachievedbeforethereisinsufficientantibodytocauseredcellclumping.

Rh-DandRh-carealwaysmeasuredandtheresultwillbegiveniniu/ml;hencethehigherthe result the worse theeffectsarelikelytobe.

Otherantibodylevelsareexpressedastitres.Atitreof1:2meansthataherasingledilutiontherewasnoclumpingoftheredcells.Thiswouldbealowlevelofantibody.Atitreof1:16statesthattherewerefourdilutionsbeforetheantibodywastooweaktoclumpcells,implyingamuchhigherlevelofantibody.Itisusefultounderstandthatajumpfrom 1:2to1:4isasingle dilution,asisajumpfrom1:16to1:32.

Whatparentsneedtoknow

Parentsneedtounderstand thepurposeofbloodgroupand redcellantibodyscreening,whatisbeingtestedfor andwhatthetestinvolves.Thiswillinvolvediscussionaboutthenatureandeffectsofredcellantibodies,howandwhentestresultswillbeavailableandthemeaningoftheresults.

Managementwhenanantibodyisdetected

Whenanantibodyisdetecteditisimportantthattherelevanceofthisisdiscussedwiththemother.Thediscussionshouldcoverthepotentialfordifficultiesincrossmatchingbloodandthepotentialforfetalorneonatalproblems.Ifsignificantantibody titresarefoundmanagementneedstobediscussed,includingtheneedforsurveillanceforfetalanaemiaandthepossibilityofintrauterinetransfusion–thiswouldusuallybedonebytheobstetricianmanagingthepregnancy.

Surveillancewilldependonthetypeofantibodyfound;forsomeantibodies,thetitre(level)oftheantibody;andthegestationofpregnancyatwhichitisdiscovered.

Discussionwiththeconsultantteamisusuallyneededtodefinethestepsthatneedtobetaken.

Whenanantibodyisdetectedthatmaycause HDNthenextstepswillusuallybe:

1.Referralfordiscussionwithanappropriateconsultant/haematologyteam.

2.Partnertesting.This istodeterminethepotentialforfetalrisk.Onlyafetusthat isantigenpositive fortheantibodyfoundcanbeatrisk.This meansthat,forinstance,ifawomanhasanti-DantibodiesandaRh-D-positive partnertherewillbea50–100%riskofproducingababywhois Rh-D-positive,dependingonwhetherthepartnercarriesoneortwoRh-D-positive genes.Itisimperativethatthewomanunderstands

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theimportanceofpartnertesting,theneedtobehonestifthere canbeanydoubtregardingpaternity(andforthistobeaskedaboutsensitively,withoutthepartnerbeingpresent).BewarewithIVFpregnanciesalso.Remembertoaskwhethertherehasbeeneggdonation,asinthesecasesitmaybethematernalgeneticcomplementthatdiffersandcases ofHDNhaveoccurredwherethisvitalfacthasnotbeenascertained.

3.FreefetalDNAtesting.Wherethefetusispotentiallyatriskbecausethepartnerispositivefortheantigentothedetectedantibodyorwherepartnertestingcannotbeundertaken,typingofthefetalredcellstatus canbeperformedonabloodtestfromthewoman.Thetest is usuallycarriedout between12–18weeks.Theresultsareaccuratein99%ofcasesbut insomecasesaresultcannotbegiven.

4.Confirmatorytesting.InvasivetestingusingCVSoramniocentesisisusuallyundertakenonlywherethereisaneedtoestablishfetalkaryotypeforotherreasons.Incaseswhereultrasoundsuggestsdevelopinganaemiaafetalbloodsamplepriortointrauterinetransfusionwillbetestedforfetalbloodtyping.

On-goingsurveillance

Oncetheriskofapregnancybeingaffectedhasbeenestablishedthetimingandfrequencyofrepeattestingofantibodytitrescanbedetermined.Theneedforassessmentofthefetusat riskcanalsobeestablished.

Surveillanceforfetal anaemiaisnowundertakenprimarilyusingultrasoundmeasurement ofthebloodflowvelocitywithinthefetalbrain.Measurement ofthemaximumvelocityinthefetalmiddlecerebralarteryhasbeenfoundtobeasaccurateastheold-fashionedmeasurementofbilirubininamnioticfluid,butiswithouttheattendantrisksofserialamniocentesis.

Thefrequencyofsurveillancewillbedeterminedbytheriskofanaemia,whichisdependentonthetypeandlevelofantibodyandtheriskofthefetusbeingantigen-positive.

Conclusion

Fetalinvestigationsareanintegralaspectof antenatalcare.Scientistsandclinicianshavedevelopeda rangeofnewdiagnosticandimagingtechnologies.Someofthesehavebeenincorporatedintonationalscreeningprogrammesandstandardsofcare.Themidwifemustthereforeensurethatwomenareinformedaboutthebenefitsandrisksassociatedwiththesetechnologies,sothattheycanmakechoicestosuittheirrequirements.Undoubtedly,testingtechnologiesprofoundlyinfluencewomen'sexperiencesofpregnancyandtheirearlyafachmenttotheirunbornchild.Midwivesthereforehaveadutytopreparewomenforteststhroughsensitiveandaccuratecommunicationsandthentosupportparentsintheirassimilationofinformationanddecision-makingoncetheresultsareknown.

Maternalinvestigationsalsorequirecarefulcounselling andthoughtasaconstellationofunintendedconsequencescanariseifwomendonotthinkthroughtheirscreeningchoices,orareinadequatelycounselled.

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