The study of Attilakos et al.1 and our own2 showed that the incidence (20–22%) of substantial scalp trauma following exposure to vacuum extraction was quite high. However, as was pointed out by Dr Vacca, no infant in the study of Attilakos et al. developed subaponeurotic haemorrhage (SAH). In our series, although 21% of infants developed SAH, less than 30% of them were of the severe type requiring vascular circulating volume expansion.
There are a number of possible explanations for this marked difference in the incidence of SAH between these two studies.
First, both studies had different objectives and therefore different study designs. Our study aimed to determine the risk factors associated with SAH following exposure to vacuum extraction in a routine clinical situation. To do that, we continued our study until we had recruited a significant number of infants with SAH. The study of Attilakos et al. aimed to compare the effectiveness of two types of vacuum cups. The number of infants with scalp injuries was therefore not large enough for them to determine the significant risk factors associated with these injuries. Second, the newborn infants in the Bristol study by Attilakos et al. were assessed by paediatric senior house officers who were relatively junior doctors and might have missed some cases of SAH. There was no named paediatric consultant as their coresearcher, and it is not certain how thoroughly neonatal scalp complications were assessed and looked for. Third, being a randomised controlled trial, a standardised protocol of application of the vacuum extractors was presumably strictly adhered to by all the doctors during the study of Attilakos et al. They reported that ‘majority of the deliveries by senior house officers were performed under direct supervision’, in their study. This was not the case in our study, which reports the results of routine clinical practice.
Dr Vacca has appropriately suggested that adverse neonatal outcome following vacuum extraction is ‘more likely to result from the way the device is used and by whom’. Development and maintenance of labour-room skills through training supported by consistent practice, exercise of good judgment and constant mindfulness of the potential risks while working under pressure are important factors in preventing complications of delivery.
Our hospital is currently completing a randomised controlled trial on the Kiwi vacuum cup versus the metal cup vacuum extractor, and we anticipate that our results will be available in the near future.