CONSULTATION DRAFT
7.1Fetaldevelopment and anatomy
Ultrasound examination between 18 and 20 weeks gestation allows assessment of fetal development and anatomy. It is also used to estimate gestational age when this has not been assessed in the first trimester.
7.1.1Background
Diagnostic ultrasound is a sophisticated electronic technology that uses pulses of high frequency sound to produce an image.This imaging can enable measurement of the baby, estimation of the gestational age and identification of structural abnormalities.Gestational age assessment and screening for chromosomal abnormalities in the first trimester are discussed in Module I of the Guidelines. This section discusses the second trimester scan to assess the development and anatomy of the baby and the position of the placenta. This assessment is also known as the morphology scan.
Congenital abnormalities in Australia
In Australia in 2010, congenital abnormality (including chromosomal and structural abnormalities) was the leading cause of perinatal death in single pregnancies (28.8%) and accounted for 76.1% of neonatal deaths of babies born at 32–36 weeks gestation and 44.1% of deaths of babies born after 37weeks gestation (Li et al 2012). Available data on neural tube defects among babies born to Aboriginal and Torres Strait Islander women show a higher overall prevalence than among non-Indigenous women (16.6 versus 7.3 per 10,000 total births in 2006–2008) (AIHW 2011).
7.1.2Offering assessment of fetal development and anatomy
Summary of the evidence
Routinely offering women an ultrasound during the second trimester to screen for fetal abnormalities and location of the placenta is recommended in the United Kingdom (NICE 2008), the United States (ACOG 2009) and Canada (Cargill et al 2009) and has been previously recommended in Australia (RANZCOG 2009). Although cervical length is increasingly reported, there is insufficient evidence to recommend its routine assessment (RANZCOG 2008; 3Centres Collaboration 2012).
Accuracy and effectiveness of ultrasound assessment of fetal development and anatomy
•Gestational age: While gestational age assessment using ultrasound is more accurate in the first trimester (Kalish et al 2004; Caughey et al 2008), some women may not have access to ultrasound until later in pregnancy. Gestational age has been successfully estimated in the second trimester (Johnsen et al 2005; Oleson & Thomsen 2006).
•Structural abnormalities: Ultrasound has been used in the second trimester to detect anomalies of the heart (Perri et al 2005; Del Bianco et al 2006; Westin et al 2006; Fadda et al 2009), renal tract (Cho et al 2005) and umbilical artery (Cristina et al 2005), neural tube defects (Norem et al 2005) and anomalies resulting from exposure to alcohol (Kfir et al 2009). The rate of detection of structural anomalies is generally higher in the second than in the first trimester (Saltvedt et al 2006; Hildebrand et al 2010).
•“Soft” markers: While the combination of nuchal thickness and biochemical markers in the first trimester is more effective in identifying chromosomal abnormalities (see Module I, Chapter 9), some markers (egechogenic bowel, short femur, short humerus, thickened nuchal fold, absent nasal bone) identified in the second trimester ultrasound occur more frequently in babies with chromosomal abnormalities (Bottalico et al 2009). A combination of markers is more accurate than a single marker alone; for example only 5% of babies with identified chromosomal abnormality had echogenic bowel as the only finding (Iruretagoyena et al 2010).
•Placenta: Second trimester ultrasound has effectively identified placental location (Cargill et al 2009), overlap of the cervical os (Robinson et al 2012), placental length (which may assist in identifying risk of having a small-for-gestational age baby) (McGinty et al 2012) and placenta praevia (which may resolve in women with [61%] and without [90%] a previous caesarean section) (Lal et al 2012).
•Type of ultrasonography: Accurate assessment can be performed using standard 2D ultrasonography. Assessment may be performed more rapidly using 3D ultrasonography (Benacerraf et al 2006; Pilu et al 2006).
Timing of ultrasound assessment of fetal development and anatomy
Recommended timing of the ultrasound scan varies in international guidelines but is generally in the range of 18–20 weeks as:
•sensitivity in detecting structural abnormalities increases after 18 weeks gestation (Cargill et al 2009); and
•detection of structural abnormalities before 20 weeks gestation gives women the choice of terminating the pregnancy, where this is permitted under jurisdictional legislation.
Ultrasound can be used to assess gestational age up to 24 weeks gestation and to detect abnormalities throughout the pregnancy.
Recommendation 4Grade B
Offer pregnant women ultrasound screening to assess fetal development and anatomy between 18and 20 weeks gestation.
Practice point b
Timing of the ultrasound will be guided by the individual situation (eg for women who are obese, visualisation may improve with gestational age).
There is no benefit from repeated ultrasound assessments unless they are clinically indicated. Repeated ultrasound assessments increase costs for the woman, may be inconvenient and have the potential to increase anxiety (eg through false positives).
Practice point c
Repeated ultrasound assessment may be appropriate for specific indications but should not be used for routine monitoring.
Other considerations
Benefits and harms
A Cochrane review (Whitworth et al 2010) found a reduced number of inductions for ‘prolonged pregnancy’ and no significant differences in birth weight, size for gestational age, Agpar scores and rates of admission to neonatal intensive care between babies exposed to ultrasound in early pregnancy (before 24 weeks) and those not exposed. There were no significant differences in growth and development, visual acuity or hearing for children aged 8–9 years (Whitworth et al 2010). Follow-up at 15–16 years (n=4,458) found no significant effect on overall school performance (Stalberg et al 2009).
No studies were identified that assessed psychological benefits or harms to the mother. Women may not be fully informed about the purpose of routine ultrasound and may be made anxious, or be inappropriately reassured by scans (Garcia et al 2002; Lalor & Devane 2007). A small systematic review found insufficient evidence to support either high or low levels of feedback during ultrasound to reduce maternal anxiety and change maternal health behaviour (smoking, alcohol use) (NabhanFaris 2010).
Who should conduct the assessment?
Minimum standards for health professionals conducting ultrasound assessments are disseminated by the Australian Society for Ultrasound in Medicine, the Australasian Sonographer Accreditation Registry, the Royal Australian and New Zealand College of Radiologists, and the Royal Australian and New Zealand College of Obstetricians and Gynaecologists.
Practice point d
Ultrasound assessment should only be performed by a person who has appropriate training.
Access to ultrasound
The costs associated with ultrasound may limit access for some women, particularly if bulk-billed services are not available in their area.
In remote regions, it may be difficult for women to access ultrasound examination due to limited availability of appropriate equipment, a lack of accredited and trained professionals in some areas and the costs involved in travelling for the assessment. It is noted that there is a lack of consistency in funding across the States and Territories to support travel and accommodation for women from rural and remote areas to access care and services.
7.1.3Discussing assessment of fetal development and anatomy
Not all women will want an ultrasound and some may not understand the purpose of the assessment or think that it is being offered because there is something wrong with the pregnancy.
In discussing the ultrasound scan, it is important to explain:
•that it is the woman’s decision whether the ultrasound takes place;
•where ultrasound services are available if the woman chooses to have one;
•that ultrasound does not detect all fetal and maternal abnormalities;
•any costs involved for the woman and the timeframe for receiving results; and
•choices if any abnormalities are detected (some parents may not want an ultrasound if there is no change in birth outcomes).
7.1.4Practice summary:fetal development and anatomy
When: Between 18 and 20 weeks.Who: Midwife; GP; obstetrician; Aboriginal and Torres Strait Islander Health Practitioner; Aboriginal and Torres Strait Islander Health Worker; multicultural health worker.
Discuss the purpose of the ultrasound: Explain that ultrasound assessment is offered to all women to check the anatomy and growth of the baby and can also be used to estimate gestational age if this has not already been done.
If a woman chooses to have an ultrasound, arrange an appointment or referral: When arranging referral, ensure that the ultrasound takes place before 20weeks of pregnancy.
Take a holistic approach: Provide advice to assist women in accessing services (egavailability of bulk-billed services and interpreters). For women who need to travel for assessment, explain the need to plan early and organise travel and accommodation. Provide information on available funding to assist with these costs.
Arrange follow-up: Routinely make sure that women are informed of the results of the scan and document these in her antenatal record. If an abnormality is suspected or identified, offer women access to appropriate counsellingand ongoing support by trained health professionals.
7.1.5Resources
Obstetric ultrasound. In: MinymakuKutjuTjukurpa Women’s Business Manual, 4th edition. Congress Alukura, Nganampa Health Council Inc and Centre for Remote Health.
RANZCOG (2010) Prenatal Screening for Fetal Abnormalities.College Statement C-Obs 35.Royal Australian and New Zealand College of Obstetricians and Gynaecologists.
7.1.6References
3 Centres Collaboration (2012) Cervical shortening and cervical insufficiency. Clinical Practice Guidelines 2011.Melbourne: Mercy Hospital for Women, Monash Medical Centre, The Royal Women’s Hospital.
ACOG (2009) Ultrasonography in pregnancy. ACOG Practice Bulletin No. 101. American College of Obstetricians and Gynecologists.ObstetGynecol113: 451–61.
AIHW (2011) Neural Tube Defects in Australia.Prevalence before Mandatory Folic Acid Fortification.Cat No PER 53. Canberra: Australian Institute of Health and Welfare.
Benacerraf BR, Shipp TD, Bromley B (2006) Three-dimensional US of the fetus: volume imaging. Radiol 238(3): 988–96.
Bottalico JN, Chen X, Tartaglia M et al (2009) Second-trimester genetic sonogram for detection of fetal chromosomal abnormalities in a community-based antenatal testing unit. Ultrasound ObstetGynecol33(2): 161–68.
Cargill Y, Morin L, Bly S et al (2009) Content of a complete routine second trimester obstetrical ultrasound examination and report.J ObstetGynaecol Can 31(3): 272–75, 276–80.
Caughey AB, Nicholson JM, Washington AE (2008) First- vs second-trimester ultrasound: the effect on pregnancy dating and perinatal outcomes. Am J ObstetGynecol 198(6): 703.e1–e6.
Cho JY, Lee YH, Toi A et al (2005) Prenatal diagnosis of horseshoe kidney by measurement of the renal pelvic angle. Ultrasound ObstetGynecol25(6): 554–58.
Cristina MP, Ana G, Inés T et al (2005) Perinatal results following the prenatal ultrasound diagnosis of single umbilical artery. ActaObstetGynecolScand 84(11): 1068–74.
Del Bianco A, Russo S, Lacerenza N et al (2006) Four chamber view plus three-vessel and trachea view for a complete evaluation of the fetal heart during the second trimester. J Perinat Med 34(4): 309–12.
Fadda GM, Capobianco G, Balata A et al (2009) Routine second trimester ultrasound screening for prenatal detection of fetal malformations in Sassari University Hospital, Italy: 23 years of experience in 42,256 pregnancies.Eur J ObstetGynecolReprodBiol144(2): 110–14.
Garcia J, Bricker L, Henderson J et al (2002) Women’s views of pregnancy ultrasound: a systematic review. Birth 29(4): 225–50.
Hildebrand E, Selbing A, Blomberg M (2010) Comparison of first and second trimester ultrasound screening for fetal anomalies in the southeast region of Sweden. ActaObstetGynecolScand 89(11): 1412–19.
Iruretagoyena JI, Bankowsky H, Heiser T et al (2010) Outcomes for fetal echogenic bowel during the second trimester ultrasound. J Matern-Fetal Neonatal Med 23(11): 1271–73.
Johnsen SL, Rasmussen S, Sollien R et al (2005) Fetal age assessment based on femur length at 10-25 weeks of gestation, and reference ranges for femur length to head circumference ratios. ActaObstetGynecolScand 84(8): 725–33.
Kalish RB, Thaler HT, Chasen ST et al (2004) First- and second-trimester ultrasound assessment of gestational age. Am J ObstetGynecol191(3): 975–78.
Kfir M, Yevtushok L, Onishchenko S et al (2009) Can prenatal ultrasound detect the effects of in-utero alcohol exposure? A pilot study.Ultrasound ObstetGynecol 33(6): 683–89.
Lal AK, Nyholm J, Wax J et al (2012) Resolution of complete placenta previa: does prior cesarean delivery matter? JUltrasound Med 31(4): 577–80.
Lalor JG & Devane D (2007) Information, knowledge and expectations of the routine ultrasound scan. Midwifery 23(1): 13–22.
Li Z, Zeki R, Hilder L et al (2012) Australia’s Mothers and Babies 2010. Sydney: Australian Institute for Health and Welfare National Perinatal Epidemiology and Statistics Unit.
McGinty P, Farah N, Dwyer VO et al (2012) Ultrasound assessment of placental function: the effectiveness of placental biometry in a low-risk population as a predictor of a small for gestational age neonate. Prenatal Diag 32(7): 620–26.
Nabhan AF & Faris MA (2010) High feedback versus low feedback of prenatal ultrasound for reducing maternal anxiety and improving maternal health behaviour in pregnancy. Cochrane Database Of Systematic Reviews (Online)(4): CD007208.
NICE (2008) Antenatal Care. Routine Care for the Healthy Pregnant Woman.National Collaborating Centre for Women’s and Children’s Health.Commissioned by the National Institute for Health and Clinical Excellence. London: RCOG Press.
Norem CT, Schoen EJ, Walton DL et al (2005) Routine ultrasonography compared with maternal serum alpha-fetoprotein for neural tube defect screening. ObstetGynecol106(4): 747–52.
Olesen AW & Thomsen SG (2006) Prediction of delivery date by sonography in the first and second trimesters.Ultrasound ObstetGynecol 28(3): 292–97.
Perri, T. (2005) Risk factors for cardiac malformations detected by fetal echocardiography in a tertiary center.JMatern-Fetal Neonatal Med (2): 123-128.
Pilu G, Segata M, Ghi T et al (2006) Diagnosis of midline anomalies of the fetal brain with the three-dimensional median view. Ultrasound ObstetGynecol 27(5): 522-529.
Randall P, Brealey S, Hahn S et al (2005) Accuracy of fetal echocardiography in the routine detection of congenital heart disease among unselected and low risk populations: a systematic review. BJOG 112(1): 24–30.
RANZCOG (2009) Pre-pregnancy Counselling and Routine Antenatal Assessment in the Absence of Pregnancy Complications (C-Obs 3).Melbourne: Royal Australian and New Zealand College of Obstetricians and Gynaecologists.
Robinson AJ, Muller PR, Allan R et al (2012) Precise mid-trimester placenta localisation: does it predict adverse outcomes? Aust NZ J ObstGynaecol 52(2): 156–60.
Saltvedt S, Almström H, Kublickas M et al (2006) Detection of malformations in chromosomally normal fetuses by routine ultrasound at 12 or 18 weeks of gestation-a randomised controlled trial in 39,572 pregnancies.BJOG 113(6): 664–74.
Stålberg K, Axelsson O, Haglund B et al (2009) Prenatal ultrasound exposure and children's school performance at age 15-16: follow-up of a randomized controlled trial. Ultrasound ObstetGynecol 34(3): 297–303.
Verburg BO, Steegers EA, de Ridder M et al (2008) New charts for ultrasound dating of pregnancy and assessment of fetal growth: longitudinal data from a population-based cohort study. Ultrasound ObstetGynecol 31(4): 388–96.
Westin M, Saltvedt S, Bergman G et al (2006) Routine ultrasound examination at 12 or 18 gestational weeks for prenatal detection of major congenital heart malformations? A randomised controlled trial comprising 36,299 fetuses.BJOG 113(6): 675–82.
Whitworth M, Bricker L, Neilson JP et al (2010) Ultrasound for fetal assessment in early pregnancy.Cochrane Database of Systematic Reviews 2010, Issue 4. Art. No.: CD007058. DOI: 10.1002/14651858.CD007058.pub2.
CONSULTATION DRAFT