Malpositions of the Occiput and Malpresentations

C H A P T E R 2 0

Malpositions of the occiput and malpresentations

Terri Coa tes

CHAPTER CONTENTS

Introduction 436

Occipitoposterior positions 436

Causes 436

Antenatal diagnosis 436

Antenatal preparation 437

Intrapartum diagnosis 438

Midwifery care 439

Manual rotation 439

Mechanism of right occipitoposterior position (long rotation) 440

Possible course and outcomes of labour 441

The birth 442

Complications 442

Face presentation 444

Causes 444

Antenatal diagnosis 445

Intrapartum diagnosis 445

Mechanism of a left mentoanterior position 445 Possible course and outcomes of labour 446 Management of labour 447

Complications 448

Brow presentation 448

Causes 449

Diagnosis 449

Management 449

Complications 449

Shoulder presentation 449

Causes 449

Antenatal diagnosis 450

Intrapartum diagnosis 450

Possible outcome 451

Complications 451

Management 451

Unstable lie 451

Causes 451

Management 452

Compound presentation 452

References 452

Introduction

Malpositions and malpresentations present the midwife with challenges of recognition and diagnosis both in the antenatal period and during labour. The midwife must ensure all examinations and discussions with the woman are documented and appropriate obstetric referral is made where a malpresentation or malposition has been found. The midwife should take time to discuss this with the women to ensure they understand what may happen and the activities that may help (Munro and Jokinen 2012).

The presenting diameters do not ﬁt well onto the cervix and therefore do not produce optimal stimulation for uterine contractions and labour. Labour with a fetus in a malposition or a malpresentation can be long, tedious and painful, requiring empathy, sustained encouragement and support for the woman and her partner. All the usual care in labour is provided, paying particular afention to comfort and hydration (see Chapter 16). The woman should be encouraged to take an active part in decision-making and must be kept informed throughout.

In labour women should be encouraged to adopt postures and positions they ﬁnd comfortable and encouraged to remain mobile. They should be supported to use coping methods to deal with their particular pafern of labour (Simkin 2010). The progress of labour may be slow so midwives should take care to avoid the use of language that may demoralize the woman and her partner. Any sign of fetal or maternal distress or delay in labour must be referred promptly to an obstetrician. Practices that are considered unhelpful include immobility and labouring on a bed, the sefing of arbitrary time limits on the various stages of labour and the early use of epidural analgesia (Munro and Jokinen 2012).

Occipitoposterior positions

Occipitoposterior (OP) positions are the most common type of malposition of the occiput and occur in approximately 10–30% of labours, but only around 5% of births (Pearl et al 1993; Ponkey et al 2003; Munro and Jokinen 2012). Women can be reassured that internal rotation to anterior positions can be expected in the majority of cases. A persistent OP position results from a failure of internal rotation or malrotation prior to birth (Gardberg et al 1998; Peregrine et al 2007). The vertex is presenting, but the occiput lies in the posterior rather than the anterior part of the pelvis. As a consequence, the fetal head is deflexed and larger diameters of the fetal skull present (Fig. 20.1).

FIG. 20.1 (A) Right occipitoposterior position. (B) Left occipitoposterior position.

Causes

The direct cause of the occipitoposterior position is ohen unknown, but it may be associated with an abnormally shaped pelvis. In an android pelvis, the forepelvis is narrow and the occiput tends to occupy the roomier hindpelvis. The oval shape of the anthropoid pelvis, with its narrow transverse diameter, favours a direct OP position.

Antenatal diagnosis

Abdominal examination

Listen to the woman, as she may complain of backache and report feeling that her baby's bottom is very high up against her ribs, as well as feeling movements across both sides of her abdomen.

On inspection

There is a saucer-shaped depression at or just below the umbilicus. This depression is created by the ‘dip’ between the head and the lower limbs of the fetus. The outline

created by the high, unengaged head can look like a full bladder (Fig. 20.2).

FIG. 20.2 Comparison of abdominal contour in (A) posterior and (B) anterior positions of the occiput.

On palpation

While the breech is easily palpated at the fundus, the back is diﬃcult to palpate as it is well out to the maternal side, sometimes almost adjacent to the maternal spine. Limbs can be felt on both sides of the midline. The head is unusually high in an OP position which is the most common cause of non-engagement in a primigravida at term. This is because the large presenting diameter, the occipitofrontal (11.5 cm), is unlikely to enter the pelvic brim until labour begins and ﬂexion occurs. The occiput and sinciput are on the same level (Figs 20.3 and 20.4). Flexion allows the engagement of the suboccipitofrontal diameter (10 cm).

FIG. 20.3 Engaging diameter of a deflexed head: occipitofrontal (OF) 11.5 cm.

FIG. 20.4 Flexion with descent of the head.

The cause of the deﬂexion is a straightening of the fetal spine against the lumbar curve of the maternal spine. This makes the fetus straighten its neck and adopt a more erect attitude.

On auscultation

The fetal back is not well ﬂexed so the chest is thrust forward, therefore the fetal heart can be heard in the midline. However, the fetal heart may be heard more easily at the flank on the same side as the back.

Antenatal preparation

There is no current evidence that suggests active changes of maternal posture will help to achieve an optimal fetal position before labour (Hunter et al 2007; Munro and Jokinen 2012). Research has shown that the woman adopting a knee–chest position several times a day may achieve temporary rotation of the fetus to an anterior position but has only a short-term eﬀect upon fetal presentation (Kariminia et al 2004; Hunter et al 2007). There i s insuﬃcient evidence to suggest that women should adopt the hands and knees posture, unless they ﬁnd it comfortable (Simkin 2010; Munro and Jokinen 2012). Further research is needed to evaluate the eﬀect of adopting a hands and knees posture on the presenting part during labour (Hunter et al 2007).

For customary antenatal assessment of fetal position Leopold's manoeuvres can be used during abdominal examination (see Chapter 10). These traditional methods of examination are only an assessment of the placement of the fetal spine and cannot estimate the direction of the fetal head. Peregrine et al (2007) used ultrasound scans to conﬁrm abdominal palpation and found that the fetal head is ohen aligned diﬀerently

within the pelvis than the fetal spine within the uterus. In other words, the fetus may have turned its head to the right or leh and the head may be anterior within the pelvis but the fetal back may palpate as lateral.

A review of current techniques used to diagnose fetal position such as Leopold's manoeuvres, the location of fetal heart sounds, vaginal examinations and presence of back pain are ohen unreliable (Simkin 2010). Failure to identify fetal position accurately can impact on the ability of the midwife to oﬀer appropriate care. Consequently it is considered that ultrasound is the most reliable way to accurately detect the fetal position (Munro and Jokinen 2012). More research studies are needed to examine the eﬃcacy of midwifery skills in diagnosing fetal malpositions and non-technological approaches to improving the birth outcome for the woman and fetus.

Intrapartum diagnosis

The large and irregularly shaped presenting circumference (Fig. 20.5) does not ﬁt well onto the cervix. This may hinder cervical ripening and predispose to a prolonged latent phase (Akmal and Paterson-Brown 2009). The contractions may also be in-coordinate. A high head predisposes to early spontaneous rupture of the membranes at an early stage of labour, which, together with an ill-ﬁfing presenting part, may result in cord prolapse (see Chapter 22).

FIG. 20.5 Presenting dimensions of a deflexed head.

The woman may complain of continuous and severe backache, worsening with contractions. However, the absence of backache does not necessarily indicate an anteriorly positioned fetus. Descent of the head can be slow even with good contractions. The woman may have a strong desire to push early in labour because the occiput is pressing on the rectum.

Vaginal examination

The ﬁndings (Fig. 20.6) will depend upon the degree of ﬂexion of the head. Locating the anterior fontanelle in the anterior part of the pelvis is diagnostic but this may be diﬃcult if caput succedaneum is present. The direction of the sagifal suture and location of the posterior fontanelle will help to conﬁrm the diagnosis. The position of the fetal head may be checked using ultrasound where reason for the delay in labour requires accurate diagnosis.

FIG. 20.6 Vaginal touch pictures in a right occipitoposterior position. (A) Anterior fontanelle felt to left and anteriorly. Sagittal suture in the right oblique diameter of the pelvis. (B) Anterior fontanelle felt to left and laterally. Sagittal suture in the transverse diameter of the pelvis. (C) Following increased flexion, the posterior fontanelle is felt to the right and anteriorly. Sagittal suture in the left oblique diameter of the pelvis. The position is now right occipitoanterior.

Midwifery care

First stage of labour

The woman may experience severe and unremifing backache, which is tiring and can be very demoralizing, especially if the progress of labour is slow. Continuous support from the midwife will help the woman and her partner to cope with the labour (Simkin 2010; Hodnef et al 2012) (see Chapter 16). The midwife can help to provide physical support such as massage and other comfort measures. Mobility should be encouraged with changes of posture and position and where possible, the use of a bath or birthing pool and other non-pharmacological measures such as transcutaneous electrical nerve stimulation (TENS) or aromatherapy. There is no evidence that the all-fours position either during pregnancy or in labour will rotate a malpositioned baby (Kariminia et al 2004; Munro and Jokinen 2012) but may help reduce persistent back pain. An exaggerated Sims position in labour may oﬀer some relief, and anecdotal evidence suggests that it may

also aid rotation of the fetal head.

The woman may experience a strong urge to push long before the cervix has become fully dilated. This is because of the pressure of the occiput on the rectum. However, if the woman pushes at this time, the cervix may become oedematous and this would further delay the onset of the second stage of labour. The urge to push may be eased by a change in position and the use of breathing techniques, inhalational analgesia or other methods to enhance relaxation. The woman's partner and the midwife can assist throughout labour with massage and physical support. The woman may choose a range of pain control methods (see Chapter 16) throughout her labour depending on the level and intensity of pain she is experiencing at that time. The midwife must ensure that any delay in labour and fetal or maternal distress are promptly recognized and appropriate referrals made (Nursing and Midwifery Council [NMC] 2012).

Second stage of labour

Full dilatation of the cervix may need to be conﬁrmed by a vaginal examination because moulding and formation of a caput succedaneum may be in view while an anterior lip of cervix remains. The second stage of labour is usually characterized by signiﬁcant anal dilatation some time before the head is visible. The midwife can encourage the woman to adopt upright positions that may help to shorten the length of the second stage and reduce the need for operative assistance (see Chapter 17). Squafing may increase the transverse diameter of the pelvic outlet which may increase the chance of a vaginal birth.

The length of the second stage of labour is usually increased when the occiput is posterior, and there is an increased likelihood of an operative birth (Pearl et al 1993; Gimovsky and Hennigan 1995). In some cases where contractions are weak and ineﬀective an oxytocin infusion may be administered to stimulate adequate contractions and achieve advancement/descent of the presenting part.

Manual rotation

Manual rotation of the head from occipitoposterior (OP) or occipitotransverse (OT) positions to an anterior position has been shown to reduce the need for assisted birth and caesarean section by correcting the fetal malposition. This will facilitate the descent of the fetal head, to encourage a spontaneous vaginal birth (Shaffer et al 2011).

There are two techniques for undertaking manual rotation either by an obstetrician or an experienced and trained midwife. Both techniques require informed consent from the woman and adequate analgesia. The woman's bladder must be empty and the cervix should be fully dilated. Either, constant pressure is exerted with the tips of the ﬁngers against the lambdoidal suture to rotate the fetal head into the occiput anterior position, or the whole hand is introduced into the birth canal and ﬁngers and thumb positioned under the lateral posterior parietal bone and the anterior parietal bone (Phipps et al 2011): the head is then rotated to the anterior position. Using either method, the rotation may take two or three contractions to complete and then should be held for two contractions whilst the woman bears down to reduce the risk of the rotation reverting