Malpositions of the occiput and malpresentations

1. Malpositions of the occiput and malpresentations Chapter 20

2. 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.

3. 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, and painful, requiring empathy, sustained encouragement and support for the woman and her partner. All the usual care in labour is provided, paying particular attention to comfort and hydration • The woman should be encouraged to take an active part in decision-making and must be kept informed throughout.

4. 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 pattern of labour • 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 setting of arbitrary time limits on the various stages of labour and the early use of epidural analgesia

5. Occipitoposterior positions • (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 • 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 • 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

7. Causes • The direct cause of the occipitoposterior position is often 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.

8. 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

10. 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 • Flexion allows the engagement of the suboccipitofrontal diameter (10 cm).

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

13. 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. • the fetal heart may be heard more easily at the flank on the same side as the back.

14. Antenatal preparation • There is no current evidence that suggests active changes of maternal posture will help to achieve an optimal fetal position before labour • 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 • Further research is needed to evaluate the effect of adopting a hands and knees posture on the presenting part during labour

15. antenatal assessment of fetal position Leopold's manoeuvres can be used during abdominal examination 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. • used ultrasound scans to confirm abdominal palpation and found that the fetal head is often 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 left and the head may be anterior within the pelvis but the fetal back may palpate as lateral.

16. 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 often unreliable • 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 of midwifery skills in diagnosing fetal malpositions and non-technological approaches to improving the birth outcome for the woman and fetus.

17. Intrapartum diagnosis • The large and irregularly shaped presenting circumference does not fit well onto the cervix. This may hinder cervical ripening and predispose to a prolonged latent phase • 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-fitting presenting part, may result in cord prolapse

19. 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.

20. Vaginal examination • The findings 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 sagittal suture • *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.

22. Midwifery care • First stage of labour • The woman may experience severe and unremitting 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

23. 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 but may help reduce persistent back pain. • An exaggerated Sims position in labour may offer some relief, and it may also aid rotation of the fetal head.

24. 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. • 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.

25. 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 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

26. 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 • Squatting may increase the transverse diameter of the pelvic outlet which may increase the chance of a vaginal birth.

27. 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 • 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.

28. 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 • 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

29. and fingers and thumb positioned under the lateral posterior parietal bone and the anterior parietal bone • 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 If a midwife is practising in a setting where operative birth is not readily available, such as in a birthing centre, this intervention may reduce maternal and neonatal morbidity and mortality

30. Malpositions and malpresentations are generally associated with a higher incidence of interventions in labour, complications and instrumental birth

31. Mechanism of right occipitoposterior position (long rotation) • The lie is longitudinal. • The attitude of the head is deflexed. • The presentation is vertex. • The position is right occipitoposterior. • The denominator is the occiput. • The presenting part is the middle or anterior area of the left parietal bone. • The occipitofrontal diameter, 11.5 cm, lies in the right oblique diameter of the pelvic brim. • The occiput points to the right sacroiliac joint and the sinciput to the left iliopectineal eminence.

36. Flexion • Descent takes place with increasing flexion. The occiput becomes the leading part. • Internal rotation of the head • The occiput reaches the pelvic floor first and rotates forwards of a circle along the right side of the pelvis to lie under the symphysis pubis. The shoulders follow, turning of a circle from the left to the right oblique diameter.

37. Crowning • The occiput escapes under the symphysis pubis and the head is crowned. • Extension • The sinciput, face and chin sweep the perineum and the head is born by a movement of extension. • Restitution • The occiput turns of a circle to the right and the head realigns itself with the shoulders.

38. Internal rotation of the shoulders • The shoulders enter the pelvis in the right oblique diameter; the anterior shoulder reaches the pelvic floor first and rotates forwards of a circle to lie under the symphysis pubis. • External rotation of the head • At the same time the occiput turns a further of a circle to the right. • Lateral flexion • The anterior shoulder escapes under the symphysis pubis, the posterior shoulder sweeps the perineum and the body is born by a movement of lateral flexion.

39. Possible course and outcomes of labour • Long internal rotation • This is the commonest outcome. With good uterine contractions producing flexion and descent of the head, the occiput will rotate forward of a circle as described above. • Short internal rotation • The term persistent occipitoposterior position indicates that the occiput fails to rotate forwards. Instead, the sinciput reaches the pelvic floor first and rotates forwards. • As a result, the occiput goes into the hollow of the sacrum. The baby is born facing the pubic bone (face to pubis).

42. Cause • Failure of flexion: the head descends without increased flexion and the sinciput becomes the leading part. It reaches the pelvic floor first and rotates forwards to lie under the symphysis pubis.

43. Diagnosis • In the first stage of labour: signs are those of any posterior position of the occiput, namely a deflexed head and a fetal heart heard in the flank or in the midline. Descent is slow. • In the second stage of labour: delay is common. On vaginal examination the anterior fontanelle is felt behind the symphysis pubis, but a large caput succedaneum may mask this. • If the pinna of the ear is felt pointing towards the woman's sacrum, this indicates a posterior position.

44. The long occipitofrontal diameter causes considerable dilatation of the anus and gaping of the vagina while the fetal head is barely visible, and the broad biparietal diameter distends the perineum and may cause excessive bulging. • As the head advances, the anterior fontanelle can be felt just behind the symphysis pubis. Consequently the fetus is born facing the pubis. Characteristic upward moulding is present with the caput succedaneum on the anterior part of the parietal bone.

46. The birth • The sinciput will first emerge from under the symphysis pubis as far as the root of the nose and the midwife maintains flexion by restraining it from escaping further than the glabella, allowing the occiput to sweep the perineum and be born. • She then extends the head by grasping it and bringing the face down from under the symphysis pubis. • Perineal trauma is common and the midwife should watch for signs of rupture in the centre of the perineum (button-hole tear). • An episiotomy may be required, owing to the larger presenting diameters.

47. Allowing the sinciput to escape as far as the glabella.

49. Grasping the head to bring the face down from under the symphysis pubis.

50. Extension of the head.FIGS 20.14–20.17 Birth of head in a persistent occipitoposterior position.