We appreciate the comments and concerns that our paper about postpartum blood loss after misoprostol-induced labour has stimulated and are pleased to respond to the constructive comments of Dr Pek Joo Teoh1 and Dr Franz Majoko.2 In relation to Dr Teoh’s letter, Sheiner et al.3 reported on 99 cases of precipitate labour, but these were mostly spontaneous rather than induced. The incidence of precipitate labour they reported was 99 in 137 171 (1 in 1386). We speculate that the reported high rate of complications, mostly traumatic, could be attributed to the factors causing the precipitate labour (for example, placental abruption) and the unexpected nature of the event (so that resuscitation was delayed, for example). In our study, although labour was significantly faster in the misoprostol group, these cases were hospitalised and were under close supervision from the onset of induction. Furthermore, few cases were precipitate according to Sheiner’s definition, that is, <3 hours between the onset of contractions and delivery. After adjusting for induction delivery interval, the misoprostol group still had a significantly higher blood loss although the level of significance was lower, suggesting an effect of misoprostol over and above the speed of the labour. In the study of Phillip et al.,4 they stated clearly that the increased blood loss with induced labour is not because of precipitate labour alone. Women might prefer short labours, but because safety is the prime concern of both women and care givers, we recommended that misoprostol be reserved for cases with a lower Bishop score to avoid iatrogenic precipitate labour and possible excessive collagenolysis resulting in tissue fragility and increased blood loss.
Dr Franz Majoko2 refers to the Cochrane review by Kelly and Tan5 in 2001 and the meta-analysis of Li et al. in 2004,6 who reported that misoprostol is more effective than oxytocin for induction of labour. In our study, we excluded cases considered poorly inducible because of a very low initial Bishop score, doubtful cephalo-pelvic relationship, sonographic evidence of fetal macrosomia or compromised biophysical profile. These strict selection criteria might have contributed to the comparable success of both methods of induction in our study.
We respect the concerns about blinding of allocation, but we did our best in this respect as oxytocin cases were given placebo tablets and misoprostol cases had a placebo infusion. Labour attendants were not informed about the active method of induction being used. An open label design would be a good idea for another study.
We did not use oxytocin augmentation in the misoprostol group, but we added a second dose of misoprostol in cases without evidence of response after 6 hours (eight cases). We accept that evaluating postpartum blood loss is difficult and that is why we measured the pre- and post-delivery haematocrit and the difference between them. The postdelivery haematocrit was measured 6 hours postpartum. Cases with haemoglobin <10 g/dl before induction were excluded and blood transfusions were given on the basis of a clinical judgement of the haemodynamic impact of blood loss.
Our management of third stage was standardised for all cases; therefore, no difference in management could explain the difference in blood loss.
The report of Phillip et al.4 was retrospective analysis, over 3 months in 1998, of heterogeneous group of cases among which at least six subgroups could be identified including spontaneous labour, oxytocin and/or misoprostol-induced or augmented labour. Their conclusion was contradictory to the hypothesis they started with, which was ‘prostaglandin induced labour is associated with lower blood loss’.
The meta-analysis of Li et al.6 was meant to evaluate the efficacy of either agent in inducing labour. The amount of postpartum blood loss was a subsidiary finding reported among the adverse effects and was not reported by many of the included studies.
Finally, we admit that the power of our study might be insufficient to detect small differences in blood loss, but logistics and time constraints influenced our sample size. We regard it primarily as a pilot study, raising issues that need to be evaluated in further larger studies.