26 Kim Hinshaw1,2 and Sabaratnam Arulkumaran3 1 Sunderland Royal Hospital, Sunderland, UK 2 University of Sunderland, Sunderland, UK 3 St George’s University of London, London, UK The vertex is a diamond‐shaped area on the fetal skull bounded by the anterior and posterior fontanelles and laterally by the parietal eminences. Vertex presentation is found in 95% of labours at term and is associated with flexion of the fetal head. Breech, brow, face and shoulder presentations constitute the remaining 5% and are collectively known as malpresentations. Their aetiology is usually unknown, but associations include macrosomia, multiparity, polyhydramnios, multiple pregnancy, placenta praevia, preterm labour, and anomalies of the uterus or pelvis (congenital or acquired, e.g. lower segment fibroids) and more rarely the fetus. The denominator is a laterally sited bony eminence on the presenting part (‘occiput’ for vertex presentation, ‘mentum’ for face, ‘acromium’ for shoulder and ‘sacrum’ for breech). The position of the presenting part is defined by the relationship of the denominator to the maternal bony pelvis. The vertex enters the pelvis in the occipito‐transverse (OT) position and during descent rotates to an occipito‐anterior (OA) position in 90% of cases. This position is associated with a well‐flexed head, allowing the smallest anteroposterior (suboccipito‐bregmatic) and lateral (biparietal) diameters to pass through the pelvis (both 9.5 cm). Malposition occurs when the occiput remains in a tranverse or posterior position as labour progresses. Persistent malposition results in deflexion with a larger anteroposterior diameter presenting (occipito‐frontal 11.5 cm). It is associated with increasing degrees of anterior or posterior asynclitism, with one of the parietal bones preceding the sagittal suture (in posterior asynclitism, the posterior parietal bone leads; Fig. 26.1). Significant degrees of asynclitism can result in labour dystocia and a higher risk of operative delivery [1]. Fig. 26.1 Posterior asynclitism of the vertex: posterior parietal bone presenting below the sagittal suture. In most cases, flexion occurs as the vertex descends onto the pelvic floor, leading to correction of the malposition and a high chance of spontaneous delivery. The level of the presenting part should be critically assessed as labour progresses. On abdominal examination, the head should descend until it is no more than 1/5 palpable in the late first stage. On vaginal examination the presenting part is assessed relative to the level of the ischial spines. Care must be taken to assess the level using the lowest bony part. Malposition is associated with increased moulding of the fetal skull and a large caput succedaneum, which may give false reassurance about the true degree of descent. In modern obstetric practice, operative vaginal delivery is not attempted if the leading edge of the skull is above the ischial spines (i.e. above ‘0’ station; Fig. 26.2). Fig. 26.2 Level of the presenting part relative to the ischial spines. The incidence of breech presentation varies according to gestation: 20% at 30 weeks falling to 4% by term. The aetiology of most breech presentations at term is unclear but known factors to consider include placenta praevia, polyhydramnios, bicornuate uterus, fibroids and, rarely, spina bifida or hydrocephaly. Between 50 and 70% of breech presentations manifest with hips flexed and knees extended (extended breech) Complete (or flexed) breech is more common in multiparous women and constitutes 5–10% at term (hips and knees flexed; Fig. 26.3). Incomplete or footling breech (10–30%) presents with one or both hips extended, or one or both feet presenting and is most strongly assoiated with cord prolapse (5–10%). Knee presentation is rare. Fig. 26.3 The common types of breech presentation. Clinical diagnosis may miss up to 20% of breech presentations, relying on identifying the head as a distinct hard spherical hard mass to one or other side under the hypochondrium which distinctly ‘ballots’. In such cases the breech is said to feel broader and an old adage reminds us: ‘Beware the deeply engaged head – it is probably a breech!’ Auscultation may locate the fetal heart above the maternal umbilicus and ultrasound confirmation should be considered. If breech presentation is suspected at 36 weeks, ultrasound assessment is recommended as it allows a comprehensive assessment of the type of breech, placental site, estimated fetal weight, confirmation of normality and exclusion of nuchal cord or hyperextension of the fetal neck. External cephalic version (ECV) is encouraged after 36 or more weeks as the chance of spontaneous version to cephalic presentation after 37 weeks is only 8%. Absolute contraindications are relatively few but include placenta praevia, bleeding within the last 7 days, abnormal cardiotocography (CTG), major uterine anomaly, ruptured membranes and multiple pregnancy [2]. Couples should receive counselling about the procedure and its success rates and complications, and the subsequent management of persistent breech presentation. Tocolysis increases the likelihood of success, with average rates of 50% (range 30–80%). Women should be made aware that even with a cephalic presentation following ECV, labour is still associated with a higher rate of obstetric intervention than when ECV has not been required. ECV should be performed in a setting where urgent caesarean section (CS) is available in case of fetal compromise during or soon after ECV. CTG for 30–40 min prior to and after ECV should provide confirmation of fetal health. The chance of success is greater with multiparity, flexed breech presentation and an adequate liquor volume. The use of moxibustion at 33–35 weeks, in combination with acupuncture, may reduce the numbers of births by CS. Training specialist midwives is potentially cost‐efficient with success rates comparable to consultant‐led services (51–66%) [3]. The first step in ECV involves disengaging the breech by moving the fetus up and away from the pelvis, shifting it to a sideways position, followed by a forward somersault to move the head to the lower pole; if this fails a backward somersault can be tried. The need for emergency delivery by CS because of suspected fetal compromise is estimated to be 0.5%. Mothers who are rhesus‐negative should have a Kleihauer–Betke test after the procedure and receive anti‐D. If ECV is unsuccessful, women who are keen to avoid CS may be offered a repeat attempt under neuraxial blockade. This increases the chances of success (58.4% vs. 43.1%; relative risk, RR 1.44, 95% CI 1.27–1.64) and reduces the incidence of CS (46.0% vs. 55.3%; RR 0.83, 95% CI 0.71–0.97) [4]. Otherwise appropriate counselling about the options of elective CS or assisted vaginal breech delivery should be offered. Despite increasing evidence supporting elective CS for breech delivery at term, controversy and debate continue among professional groups. For women who wish to deliver vaginally, antenatal selection aims to ensure optimal outcome for mother and baby but remains relatively subjective. Women with frank and complete breech presentations (fetal weight <4000 g) encounter minimal problems, while those with footling breech are advised elective CS because of the increased risk of cord prolapse. CT or X‐ray pelvimetry do not appear to improve outcome. Spontaneous onset of labour is preferred and labour management is similar to vertex presentation. Successful outcome depends on a normal rate of cervical dilatation, descent of the breech and a normal fetal heart rate (FHR) pattern. Where progress of labour is poor and uterine contractions are inadequate, oxytocin augmentation can be used juidiciously with early resort to emergency CS if progress remains slow (<0.5 cm/hour), particularly in the late first stage. Epidural anaesthesia prevents bearing down before the cervix is fully dilated and is particularly important for labour with a preterm breech, when there is a real risk of head entrapment in the incompletely dilated cervix if pushing commences too early. For all breech labours, the mother should be encouraged to avoid bearing down for as long as possible. It is best to wait until the anterior buttock and anus of the baby are in view over the mother’s perineum, with no retraction between contractions. Classically, the mother’s legs are supported in the lithotomy position (the alternative upright breech technique is described later). Primigravidae will usually require an episiotomy with appropriate analgesia, although multigravidae can be assessed as the perineum stretches up. The buttocks deliver in the sacro‐tranverse position. The mother should be encouraged to push with contractions, aiming for an unassisted delivery up to and beyond the level of the umbilicus. There is no need to pull down a loop of cord. The accoucheur should sit with hands ready, but resting on their own legs. Assistance is only required if the legs do not deliver. Gentle abduction of the fetal thigh whilst hyperflexing the hip, followed by flexing the lower leg at the knee will release the foot and leg (Fig. 26.4). Fig. 26.4 Delivery of extended legs by gentle abduction of the thigh with hyperflexion at the hip, followed by flexion at the knee: (a) right leg; (b) left leg. When the scapulae are visible with the arms flexed in front of the chest, sweep each arm around the side of the fetal chest to deliver using a finger placed along the length of the humerus. If the scapulae are not easily seen or if the arms are not easily reached, they may be extended above the shoulders. This can be resolved using the Løvset manoeuvre. Fig. 26.5 Løvset’s manoeuvre for extended arms: (a) rotation to bring the posterior (left) arm to the front followed by (b) delivery of the left arm (now anterior) from under the pubic ramus. Nuchal displacement (an arm trapped behind the fetal neck) is rare. If the left arm is trapped, the baby will need to be rotated in a clockwise direction to ‘unwrap’ the arm so that it can be reached. If the right arm is involved, anticlockwise rotation is needed. Allow the head to descend into the pelvis, assisted by the weight of the fetus until the nape of the neck is visible under the symphysis pubis. Ensure slow controlled delivery of the head using one of four methods. Fig. 26.6 Delivery of the head using the Mauriceau–Smellie–Veit manoeuvre assisted by suprapubic pressure. This rare complication occurs in two situations. Women should be intimately involved in decisions about mode of breech delivery and the available evidence presented appropriately. A senior midwife or a doctor experienced in assisted breech delivery must be present. As vaginal breech deliveries decline, developing expertise in breech delivery now relies on simulation training and experience of breech delivery at CS. Brow presentation occurs in 1 in 1500–3000 deliveries. The head is partially deflexed (extended), with the largest diameter of the head presenting (mento‐vertical, 13.5 cm). The forehead is the lowest presenting part but diagnosis relies on identifying the prominent orbital ridges lying laterally. The eyeballs and nasal bridge may just be palpated lateral to the orbital ridges. Position is defined using the frontal bone as the denominator (i.e. ‘fronto‐‘). Persistent brow presentation results in true disproportion, but when diagnosed in early labour careful assessment of progress is appropriate. Flexion to vertex or further extension to face presentation occurs in 50% and vaginal delivery is possible. Cautious augmentation with oxytocin should only be considered in nulliparous patients for delay in the early active phase of labour. If brow presentation persists, emergency CS is recommended. Vaginal delivery of a brow presentation is possible in extreme prematurity. Preterm labour is best managed in the same way as term labour, with delivery by CS if progress slows or arrests. Cord prolapse is more common and, though rare, uterine rupture can occur in neglected labour or with injudicious use of oxytocin. For this reason labour should not be augmented in multigravid patients with a confirmed brow presentation if progress is inadequate. Face presentation occurs in 1 in 500–800 labours. The general causes of malpresentation apply for face presentation, but fetal anomalies (neck or thyroid masses, hydrocephalus and anencephaly) should be excluded. The fetal head is hyperextended and the occiput may be felt higher and more prominently on the same side as the fetal spine. However, face presentation is rarely diagnosed antenatally. On vaginal examination in labour, diagnosis relies on feeling the mouth, malar bones, nose and orbital ridges. Position is defined using the chin or mentum as the denominator. The mouth and malar bones form a triangle which can help differentiate face presentation from breech, where the anus lies in a straight line between the prominent ischial tuberosities. Face presentation is often first diagnosed in late labour. The submento‐bregmatic diameter (9.5 cm) is compatible with normal delivery but only with the fetus in a mento‐anterior position (60%) (Fig. 26.7). The same diameter presents with a persistent mento‐posterior position (25%) but this cannot deliver vaginally as the fetal neck is maximally extended. Fetal scalp clips, blood sampling and vacuum extraction are absolutely contraindicated. Forceps delivery from low cavity can be undertaken for mento‐anterior or mento‐lateral positions by an experienced accoucheur but CS may still be required when descent is poor. Fig. 26.7 The anteroposterior submento‐bregmatic diameter of face presentation. The incidence of shoulder presentation at term is 1 in 200 and is found with a transverse or oblique lie. Multiparity (uterine laxity) and prematurity are common associations and placenta praevia must be excluded. The lie will usually correct spontaneously before labour as uterine tone increases, although prolapse of the cord or arm is a significant risk if membranes rupture early. For this reason, hospital admission from 38 weeks is recommended for persistent transverse lie. External version can be offered (and may also be considered for transverse lie presenting in very early labour). On vaginal examination, the denominator is the acromium but defining position can be difficult. If membrane rupture occurs at term with the uterus actively contracting, delivery by CS should be undertaken promptly to avoid an impacted transverse lie. If the uterus is found to be moulded around the fetus, a classical CS is recommended to avoid both fetal and maternal trauma. In cases of intrauterine death with a transverse lie, spontaneous vaginal delivery is possible for early preterm fetuses by extreme flexion of the body (spontaneous evolution). However, CS will usually be required beyond mid‐trimester, although a lower segment approach may be used. In higher‐income countries, cephalopelvic disproportion is usually ‘relative’ and due to persistent malposition or relative fetal size (macrosomia). Classically we consider these problems with regard to the passage, the passenger or the powers, either alone or in combination. Absolute disproportion due to a contracted pelvis is now rare in higher‐income countries unless caused by severe pelvic trauma and this should be known before the onset of labour. Caldwell and Moloy described four types of pelvis: gynaecoid (ovoid inlet, widest transversely, 50%), anthropoid (ovoid inlet, widest anteroposterior, 25%), android (heart‐shaped inlet, funnel‐shaped, 20%) and platypelloid (flattened gynaecoid, 3%). These can influence labour outcome but as pelvimetry is rarely used and clinical assessment of pelvic shape is inaccurate, this rarely influences clinical mangement in labour. The anthropoid pelvis is associated with a higher risk of persistent occipito‐posterior (OP) position and relative disproportion. Fetal anomalies (e.g. hydrocephalus, ascites) where disproportion may be a problem in labour are usually assessed antenatally and delivery by elective CS considered. Fetal macrosomia is increasing, related to the rising body mass index (BMI) in many pregnant populations. The evidence for inducing non‐diabetic women with an estimated fetal weight above the 90th centile (or >4000 g) in order to reduce cephalopelvic disproportion remains equivocal. Malposition is an increasingly common cause of disproportion and may be related to a sedentary lifestyle. OP position is associated with deflexion and/or asynclitism with a larger diameter presenting. Optimal uterine activity will correct the malposition in 75% of cases. Flexion occurs as the occiput reaches the pelvic floor with long rotation through 135° to an OA position and a high chance of normal delivery. Moulding of the fetal skull and pelvic elasticity (related to changes at the symphysis pubis) are dynamic changes that facilitate progress in labour and delivery. Short rotation through 45° to direct OP can result in spontaneous ‘face to pubes’ delivery, although episiotomy may be required to allow the occiput to deliver. Persistent OP position occurs in up to 25% of cases and is associated with further deflexion. The risk of assisted delivery is high because of relative disproportion as the presenting skull diameters increase. Delivery in the OP position from mid‐cavity (0 to +2 station) requires critical assessment to decide whether delivery should be attempted vaginally or abdominally and is discussed in later sections. Disproportion is intimately related to dystocia and failure to progress in labour. National Institute for Health and Care Excellence (NICE) guidelines recommend that first stage delay is suspected with cervical dilatation of less than 2 cm in 4 hours when forewater amniotomy should be offered. Delay is confirmed if progress is less than 1 cm 2 hours later and oxytocin augmentation should be offered [6]. This shortens labour but does not affect operative delivery rates. High‐dose oxytocin may reduce CS rates but larger trials are required before these regimens are used routinely. The decision to use oxytocin in labour arrest in multigravid patients must only be made by the most senior obstetrician and should always be approached with extreme caution as uterine rupture is a possible consequence. In the second stage, particularly with epidural analgesia, passive descent for at least 1 hour is recommended, and possibly longer if the woman wishes, before encouraging active pushing. With regional analgesia and a normal FHR pattern, birth should occur within 4 hours of full dilatation regardless of parity [7]. Oxytocin may be commenced in nulliparous patients in the passive phase if contractions are felt to be inadequate and particularly with the persistent OP position. Failure of second‐stage descent combined with excessive caput or moulding suggests disproportion and requires critical assessment to decide the appropriate mode of delivery. The incidence of instrumental vaginal delivery (IVD) varies widely and in Europe ranges from 0.5% (Romania) to 16.4% (Ireland), although there is no direct relationship with CS rates [8,9]. Epidural analgesia is associated with higher IVD rates. Allowing a longer passive second stage for descent results in less rotational deliveries and possibly a reduction in second‐stage CS [10,11]. Common indications for IVD include delay in the second stage of labour due to inadequate uterine activity, malposition with relative disproportion, maternal exhaustion and fetal compromise. Women with severe cardiac, respiratory or hypertensive disease or intracranial pathology may require IVD to shorten the second stage (when forceps may be preferred). The condition of the mother and fetus and the progress of labour should be assessed prior to performing IVD. Personal introductions to the woman and her partner are essential, explaining the reason for IVD and ensuring a chaperone and enough support are available. The findings, plan of action and the procedure itself should be explained and the discussions carefully recorded. Verbal or written consent is obtained. The mother and her partner may be physically and emotionally exhausted and great care should be exercised in terms of behaviour, communication and medical action. On abdominal examination, the fetal head should be no more than 1/5 palpable (preferably 0/5). A scaphoid shape to the lower abdomen may indicate an OP position. The FHR pattern should be assessed, noting any clinical signs of fetal compromise (e.g. fresh meconium). With acute fetal compromise (e.g. profound bradycardia, cord prolapse) delivery must be expedited urgently and this may only allow a brief explanation to be given to the patient and her partner at the time. If contractions are felt to be infrequent or short‐lasting, an oxytocin infusion should be considered in the absence of signs of fetal compromise. Both vacuum and forceps deliveries are associated with an almost threefold increased risk of shoulder dystocia compared with spontaneous delivery and this should be anticipated. However, it remains unclear whether this increased incidence is a cause or effect phenomenon [12]. On vaginal examination the cervix should be fully dilated with membranes absent. The colour and amount of amniotic fluid is recorded. Excessive caput or moulding may suggest the possibility of disproportion. Inability to reduce overlapping skull bones with gentle pressure is designated ‘moulding +++’; overlapping that reduces by gentle digital pressure is ‘moulding ++’, and meeting of the bones without overlap is ‘moulding +’. Identification of position, station, degree of deflexion and asynclitism will help decide whether IVD is appropriate, where it should be undertaken and who should undertake the procedure. Successful IVD is associated with station below the spines and progressive descent with pushing. If the head is 1/5 palpable abdominally, the leading bony part of the head is at the level of the ischial spines (mid‐cavity). When the head is more than 1/5 palpable and/or when station is above the spines, delivery by CS is recommended. Position is determined by identification of suture lines and fontanelles. The small posterior fontanelle (PF) lies at the Y‐shaped junction of the sagittal and lambdoidal sutures but may be difficult to feel when there is marked caput. The anterior fontanelle (AF) is a larger diamond‐shaped depression at the junction of the two parietal and two frontal bones. It can be differentiated from the PF by identifying the four sutures leading into the fontanelle. In deflexion (particularly OP positions) the AF lies centrally and is easily felt. Position can be confirmed by reaching for the pinna of the fetal ear, which can be flicked forwards indicating that the occiput lies in the opposite direction. Reaching the ear suggests descent below the mid‐pelvic strait. The degree of asynclitism should be assessed (see Fig. 26.1), with increasing degrees suggesting disproportion and a potentially more difficult IVD. Assessment of level and position can be difficult with OP position and in obesity. If there is any doubt after careful clinical examination, ultrasound assessment is recommended. The fetal orbits are sought and the position of the spine is noted. This is simple to do and can reduce the incorrect diagnosis of fetal position without delaying delivery, although on its own may not reduce morbidity associated with IVD [13]. IVD is normally performed with the mother in the dorsal semi‐upright position with legs flexed and abducted, supported by lithotomy poles or similar. The procedure is performed with good light and ideally aseptic conditions. The vulva and perineum should be cleansed and the bladder catheterized if the woman is unable to void. Adequate analgesia is essential and requires careful individualized assessment. Epidural anaesthesia is advisable for mid‐cavity IVD (i.e. station 0 to +2 cm below the ischial spines; see Fig. 26.2). In the absence of a pre‐existing epidural, spinal anaesthesia may be considered. IVD at station +2 cm or below is termed ‘low‐cavity’ and regional or pudendal block with local perineal infiltration (20 mL 1% plain lidocaine) can be used. Outlet IVD is performed when the head is on or near the perineum with the scalp visible without separating the labia. Descent to this level is associated with an OA position requiring minimal or no rotation and perineal infiltration with pudendal anaesthesia is effective. When the vertex is below the spines, IVD is carried out with different types of forceps or vacuum equipment, depending on the position and station of the vertex and the familiarity and experience of the doctor. Overall, comparing outcomes is easier if designation is by station and position at the time of instrumentation (e.g. left OP at +3) rather than simply mid, low or outlet IVD [11,14]. The choice of instrument depends on the operator’s experience, familiarity with the instrument, station and position of the vertex. Therefore, knowledge of the station and the position of the vertex is essential. The fetus in an OA position in the mid/low cavity can be delivered using non‐rotational, long or short‐handled forceps or a vacuum device: silicone, plastic or anterior metal cups (with suction tubing arising from the dorsum of the cup) are all suitable. For the fetus lying OT at mid‐ or low‐cavity, or lying OP position mid‐cavity, Kielland’s forceps or vacuum devices can be used to correct the malposition. Manual rotation is another technique to consider. Low‐cavity direct OP positions can be delivered ‘face to pubis’ but this may cause signifcant perineal trauma as the occiput delivers. For this reason, an OP vacuum cup (with the suction tubing arising from the edge of the cup) may be preferred. The cup will promote flexion and late rotation to OA often occurs on the perineum just prior to delivery. The Kiwi OmniCup® is an all‐purpose disposable vacuum delivery system with a plastic cup and in‐built PalmPump™ suitable for use in all positions of the vertex. Later models also display force traction to help the accoucheur avoid cup slippage (http://clinicalinnovations.com/portfolio‐items/kiwi‐complete‐vacuum‐delivery‐system/) Forceps come in pairs and most have fenestrated blades with a cephalic and pelvic curve between the heel and toe (distal end) of each blade. The heel continues as a shank which ends in the handle. The handles of the two blades sit together and meet at the lock. The cephalic curve fits along either side of the fetal head with the blades lying on the maxilla or malar eminences in the line of the mento‐vertical diameter (Fig. 26.8a). When correctly attached, uniform pressure is applied to the head, with the main traction force applied over the malar eminences. The shanks are over the flexion point, allowing effective traction in the correct direction. Non‐rotational forceps (the longer‐handled Neville Barnes or Simpson, and the shorter‐handled Wrigley’s) have a distinct pelvic curve that allows the blades to lie in the line of the pelvic axis whilst the handles remain horizontal. Kielland’s forceps have a minimal pelvic curve to allow rotation within the pelvis to correct malposition. Fig. 26.8 (a) Malar forceps application showing mento‐vertical diameter; (b) forceps traction (Pajot’s manoeuvre). Prior to applying forceps, the blades should be assembled to check whether they fit together as a pair. All forceps have matching numbers imprinted on the handles or shanks and these should also be checked. Non‐rotational forceps can be applied when the vertex is no more than 45° either side of the direct OA position (i.e. right OA to left OA). Application and delivery in a direct OP position is also possible but not routinely recommended because of increased perineal trauma. The left blade is inserted first using a light ‘pencil grip’, negotiating the pelvic and cephalic curves with a curved movement of the blade between the fetal head and the operator’s right hand, which is kept along the left vaginal wall for protection. Hands are swapped to insert the right blade using the same technique. Correct application results in the handles lying horizontally, right on top of left, and locking should be easy. Before applying traction, correct application must be confirmed: (i) the sagittal suture is lying midline, equidistant from and parallel to the blades; (ii) the occiput is no more than 2–3 cm above the level of the shanks (i.e. head well‐flexed); and (iii) no more than a fingertip passes into the fenestration at the heel of the blade. From mid‐ and low‐cavity, Pajot’s maneouvre should be used, balancing outward traction with one hand with downward pressure on the shanks with the other (Fig. 26.8b, white arrow). The handles are kept horizontal to avoid trauma to the anterior vaginal wall from the toes of the blades. Traction is synchronized with contractions and maternal effort, and the resultant movement is outwards down the line of the pelvic axis until the head is crowning. An episiotomy is usually needed as the perineum stretches up. The direction of traction is now upwards once the biparietal eminences emerge under the pubic arch and the head is born by extension. The mother will usually ask to have her baby handed to her immediately (unless active resuscitation is required). After completing the third stage, any perineal trauma is repaired and a full surgical count completed. The procedure, including plans for analgesia and bladder care, should be fully documented. Kielland’s forceps have a minimal pelvic curve allowing rotation of the head at mid‐cavity. They are powerful forceps requiring a skilled accoucheur who is willing to abandon the procedure if progress is not as expected. The number of units able to teach use of Kielland’s forceps to the point of independent practice is declining in the UK. The forceps should match and are applied so that the knobs on the handles face the fetal occiput. Kielland’s are used to correct both OT and OP positions using two methods of application. If application is difficult or the blades do not easily lock, the procedure should be abandoned. Correct application should be confirmed. Once locked, it is essential to hold the handles at a relatively steep angle downwards in the line of the mid‐pelvic axis in order to achieve easy rotation. Asynclitism is corrected using the sliding lock, moving the shanks over each other until the knobs are aligned. Rotation should take place between contractions, using only gentle force. Rotation may require the fetal head to be gently disimpacted, either upwards or downwards but no more than 1‐cm displacement is needed. Correct application should be checked again after rotation. Traction should result in progressive descent and an episiotomy is usually required. At the point of delivery, the handles of Kielland’s are only just above the horizontal because of the lack of pelvic curve. If there is no descent with traction during three contractions with maternal effort, the procedure should be abandoned. Whether Kielland’s delivery takes place in the delivery room or in obstetric theatre requires careful assessment of fetal and maternal condition, analgesia and labour progress. If there is any doubt, a formal trial of forceps should be arranged. Ventouse or vacuum delivery is increasingly favoured over forceps delivery for similar indications in the second stage of labour. The prerequisites to be satisfied before vacuum delivery are the same as for all forms of IVD. Vacuum delivery is contraindicated below 34+0 weeks and should be used with caution between 34+0 to 36+0 weeks [11]. Overall it is contraindicated for fetuses with possible haemorrhagic tendencies (risk of subgaleal haemorrhage) and before full dilatation [11]. Experienced practitioners may consider vacuum after 8 cm in a multigravid patient in some circumstances. There are many types of vacuum cup in regular use, made of different materials and of differing shapes. Whichever cup is used, the aim is to ensure that the centre of the cup is directly over the flexion point. The flexion point is 3 cm in front of the occiput in the midline and is the point where the mento‐vertical diameter exits the fetal skull [15]. Traction on this point promotes flexion, presenting the smallest diameters for descent through the pelvis: this is the optimum flexing median application (Fig. 26.9a). Other applications increase the risk of cup detachment, failed vacuum delivery and scalp trauma. In decreasing order of effectiveness, these are the flexing paramedian application (Fig. 26.9b), the deflexing median application (Fig. 26.9c) and the deflexing paramedian application (Fig. 26.9d). Fig. 26.9 Placement of the vacuum cup, from most favourable (a) to unfavourable (d). (a) Flexing median; (b) flexing paramedian; (c) deflexing median; (d) deflexing paramedian. It is vitally important to select the correct cup and this will vary depending on both the position and attitude of the fetus. The soft Silc, Silastic or anterior metal cups (where the tubing is attached on the dorsum of the cup) are not suitable for OT or OP positions, as their shape and configuration do not allow application over the flexion point. They are suitable for OA positions where the flexion point is accessible in the midline. Metal cups come in different sizes, usually 4, 5 or 6 cm in diameter. In a systematic review they were more likely to result in successful vaginal birth than soft cups (RR 1.63, 95% CI 1.17–2.28), but with more cases of scalp injury (RR 0.67, 95% CI 0.53–0.86) and cephalhaematoma (RR 0.61, 95% CI 0.39–0.95) [16]. A specially designed cup should be used for OT and OP positions: metal OP cups have tubing emerging from the lateral aspect of the cup and the Kiwi OmniCup has a groove in the dorsum of the cup to accommodate the flexible stem. These cups can be manoeuvred more laterally or posteriorly to reach the flexion point. Hand‐held vacuum is associated with more failures than metal ventouse [16], although a larger study suggested that the OmniCup has an overall failure rate of 12.9% [11]. Aldo Vacca (1941–2014) was the doyen of vacuum delivery and (with reference to the flexion point and cup application) his favourite quote was ‘It’s always more posterior than you think’. After ensuring flexion point application, the cup must be held firmly on the fetal scalp, and a finger should be run around the rim to ensure that no maternal tissue is entrapped. A vacuum of 0.2 bar (150 mmHg or 0.2 kg/cm2 negative pressure) is created using a hand‐held or mechanical pump, before rechecking the position over the flexion point and confirming maternal tissue is not trapped. The vacuum is increased to 0.7–0.8 bar (500–600 mmHg or 0.8 kg/cm2) in one step, waiting 2 min where possible to develop the ‘chignon’ within the cup. Axial traction in the line of the pelvic axis should be timed with uterine contractions and maternal pushing. A thumb should be placed on the cup, with the index finger on the scalp at the edge of the cup allowing the operator to feel any potential detachment before it is heard (by which point it is often too late to prevent detachment). Descent promotes auto‐rotation of the head to the OA position and episiotomy is often not required. Parents should be reassured that the ‘chignon’ will settle over 2–3 days. Manual rotation for persistent OP position is an alternative to IVD. The procedure requires insertion of one hand into the posterior vagina to encourage flexion and rotation. Careful patient selection is essential and the operator must ensure that effective analgesia is in place. The right hand is inserted for a left OP position (insert left hand for right OP). Four fingers are placed behind the fetal occiput to act as the ‘gutter’ on which the head will rotate, with the thumb placed alongside the anterior fontanelle. When the mother pushes with a contraction, the thumb applies pressure to flex the head and rotation to an OA position should occur with minimal effort. In a series (N = 61) where OP position was managed in two groups, the spontaneous delivery rate increased from 27% to 77% in the group offered digital rotation (P <0.0001) [17]. In a Cochrane review of 32 studies (N = 6597), forceps were less likely to fail to achieve a vaginal birth compared with ventouse (RR 0.65, 95% CI 0.45–0.94) [16]. Vaginal and perineal lacerations, including third‐ and fourth‐degree tears, are more common with forceps than with vacuum. Infra‐levator haematomas may occur occasionally and these should be drained if large or symptomatic. The risk of flatus incontinence or altered continence is also higher. Follow‐up of women who have had low or outlet IVD confirms normal physical and neourological outcomes for the vast majority of the newborn. In terms of neonatal outcome, cephalhaematoma is more common with vacuum but risk of facial injury is less. Facial and scalp abrasions are usually minor and heal in a few days. Unilateral facial nerve palsy is rare and resolves within days or weeks and is not usually related to poor technique. Skull fracture is rare and most need no treatment unless depressed, when surgical elevation may be indicated. Vacuum delivery may result in retinal haemorrhages, haematoma confined to one of the skull bones and neonatal jaundice. Severe scalp lacerations imply poor technique and are fortunately rare. Subgaleal haemorrhage may cause minor or severe morbidity and rarely mortality [18]. In reviewing morbidity associated with IVD, it is important to remember that the alternative option of second‐stage CS is also associated with increased morbidity for both mother and baby. For all IVDs, the procedure should be abandoned if there is ‘no evidence of progressive descent with moderate traction during each contraction, or where delivery is not imminent following three contractions of a correctly applied instrument by an experienced operator’ [11]. Sequential instrumentation is associated with increased neonatal morbidity and the decision to proceed must take into account the relative risks of delivery by second‐stage CS from deep in the pelvis. It can be difficult to judge whether to proceed with IVD, especially in cases with mid‐cavity malposition at the level of the ischial spines. In such cases a trial of instrumental delivery should be undertaken in theatre under regional anaesthesia, with the full theatre team and neonatal practitioner present. The estimated incidence of trial of instrumental delivery is 2–5%. It is vital to maintain awareness of the situation, with a clear willingness to abandon the attempt if progress is not as expected, proceeding immediately to CS. The couple should be advised of this strategy and appropriate consent obtained prior to the procedure, which should be undertaken by the most senior obstetrician available. In the presence of fetal compromise, it is prudent to consider delivery by emergency CS, rather than proceeding with a potentially difficult IVD. Paired cord blood samples should be taken and results recorded after every attempted IVD. New methods are being developed to achieve IVD and include disposable plastic forceps with the ability to measure traction force (see http://www.medipex.co.uk/success‐stories/pro‐nata‐yorkshire‐obstetric‐forceps/ and Fig. 26.10) and the Odon device where traction is applied using a plastic bag placed around the fetal head and neck. This device is undergoing trials led by the World Health Organization (see http://www.who.int/reproductivehealth/topics/maternal_perinatal/odon_device/en/). Fig. 26.10 Pro‐Nata Yorkshire obstetric forceps. Reproduced with permission of Mark Jessup.
Malpresentation, Malposition, Cephalopelvic Disproportion and Obstetric Procedures
Malpresentation, malposition and cephalopelvic disproportion
Definitions
Malpresentations
Breech presentation
Types of breech presentation
Antenatal management
Deciding mode of delivery
Conducting a vaginal breech delivery
Entrapment of the aftercoming head
Brow presentation
Face presentation
Shoulder presentation
Malposition and cephalopelvic disproportion
The passage
The passenger and OP malposition
The powers
Instrumental vaginal deliveries
Background
Assessment and preparation for IVD
Choice of instruments: forceps or ventouse
Forceps delivery
Rotational forceps
Vacuum delivery
Manual rotation
Complications of IVD
Safe practice: sequential intrumentation and trial of instrumental delivery
Contemporary developments in IVD
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