Shoulder dystocia

The continued interest in the management of shoulder dystocia is demonstrated by the number of papers on the subject in recent issues of the Journal of Obstetrics and Gynaecology. It is timely that attention has been drawn, yet again, to the inadequate diagnostic criteria used in many series. Mahran et al. (2008) noted that in the past, the diagnosis of shoulder dystocia only relied on the birth attendant's opinion. Now, the most common definition used specifies that shoulder dystocia has only occurred if special manoeuvres were required. However, it is quite possible for an inexperienced accoucher to utilise, for example, McRoberts manoeuvre unnecessarily and a false diagnosis is then recorded – albeit with a satisfactory outcome. Mahran and his co-workers (2008) also noted an increase in the diagnosis of shoulder dystocia, but a marked reduction in those with a poor outcome. They suggest that this is more likely due to an over-diagnosis of the condition rather than an improvement in management. They go on to suggest that pre-existing risk factors should be included in the diagnostic criteria.

Solcymani Majd et al. (2008) in their series of cases of shoulder dystocia from a district general hospital emphasised the need for meticulous documentation (as stressed in the RCOG 2005 guidelines), as they found in their series of 96 cases documentation was suboptimal in most of the 18% of their babies who needed admission to the special care baby unit, about one-quarter had brachial plexus injuries or factures. The authors also made a strong plea for universal postnatal debriefing, and were disappointed to find that it only occurred in 16% of their cases. In 4% of cases, episiotomy was the only intervention needed to facilitate delivery, perhaps suggesting overdiagnosis.

Perhaps the most important recent paper is that of Sandmire et al. (2008). They review existing theories for the aetiology of brachial plexus injuries (BPI) noting that excessive lateral traction by the obstetrician as a major cause of BPI has little convincing evidence to support it. They then advance the attractive hypothesis that the major cause is the twisting and extension of the fetal head, which can occur as a result of the natural forces of labour. This paper also contains a clear and concise description of the mechanism of normal labour in the delivery of the shoulders. This has become a neglected area in the teaching of practical obstetrics to medical students and few of the junior staff now really understand the mechanism of normal labour, and the abnormalities that may develop.

The medico legal importance of their paper is clear, there is a logical and convincing explanation for the brachial plexus injury which does not involve the excessive use of force by the birth attendants. While it must be accepted that some cases of brachial plexus trauma do involve excessive force (especially with lateral traction and lateral flexion of the head), it is reasonable to suspect that BPI is due to the normal forces of labour where there has been prolonged labour, persistent occipitoposterior position, instrumental delivery or maternal diabetes. Damage to the posterior shoulder is unlikely to be caused by excess force and strongly suggests that it is the result of forces of labour. In cases of litigation, defence against malpractice depends to a large extend on immaculate and detailed case records (Noble 2006). Documentation is so often inadequate, it may be of help to use the reporting form suggested in the RCOG guidelines (2005).

A controversial area that still exists is the need for episiotomy. The pneumonic HELPERR is widely used and understood. The E has conventionally been used to indicate episiotomy. The recent RCOG and Advanced Life Support in Obstetrics (ALSO) suddenly changed this to ‘Episiotomy should be considered but is not mandatory’ Hinshaw (2003). It is true that in many cases, an episiotomy has been carried out for delivery of the head, especially if there was an instrumental delivery. In some cases, the perineum will already be torn. However, if the perineum is intact and the head delivered, what are the criteria to suggest that an episiotomy should or should not be done? I know of none. The guidelines also stress the difficulty in performing an episiotomy in these circumstances – but this has not been my experience nor is it mentioned in any previous papers on the subject when episiotomy was advocated.

The RCOG guidelines do not produce any solid evidence to back up their statement, only ‘evidence obtained from expert committee reports or opinions of respected authorities’ (Level IV evidence). The statement of Sriemevan et al. (2000) seems more logical: ‘A large episiotomy should be cut. This makes more space for the upper trunk to move posteriorly, takes much of the pressure off the fetal neck, helps to diminish fetal cerebral engorgement and also creates more room if intravaginal manipulation is required’.

There is also the protection of the mother's perineum from major trauma. In the largest published series on the value of episiotomy (284,783 vaginal deliveries) de Leeuw et al. (2001) concluded that mediolateral episiotomy protects strongly against the occurrence of 3rd- and 4th-degree tears. Their series included 1,180 cases where there was intervention for shoulder dystocia with 46 (3.89%) cases of 3rd-degree tears. As they point out, all types of assisted vaginal delivery were associated with an increase in the risk of 3rd-degree ruptures. When discussing medico-legal aspects of episiotomy, Johnson (2005) advocated a large episiotomy. This statement was criticised by the chairman of the audit committee because RCOG guidelines did not recommend episiotomy as first-line or indeed a necessary part of shoulder dystocia management. No further evidence was offered. It does suggest that it is so because I say it is so! She goes even further to say ‘we are long past the point where an individual's personal opinion should either dictate clinical practice or the outcome of the medico-legal process’. Perhaps the time is ripe for the College to reconsider this aspect of their guidelines. One final comment on this subject, from a PACE review by Neill and Thornton (2000) ‘although shoulder dystocia is a bony problem rather than a soft tissue obstruction an episiotomy may create more space. This procedure increases the chances of delivering the anterior shoulder under the symphysis’. Moreover, it provides greater access to the pelvis if additional manoeuvres are required, and it protects the pelvic floor (Coates 1997).

One final neglected area in relation to shoulder dystocia is uterine activity. It must be remembered that the mechanism of labour is driven by uterine contractions. These may be weak and irregular if labour has been prolonged. Attempts to pull out the baby in the absence of contractions invites both fetal trauma and postpartum haemorrhage.