Journal Club on the Run - Edition #30 (01.07.24)
Summary
Fetal macrosomia is a growing problem in obstetrics in part because of the increasing prevalence of major risk factors: maternal obesity, increasing maternal age and diabetes. Fetal macrosomia is important because of the increased risk of long term disability due to birth trauma, particularly shoulder dystocia. Maternal risks in labour include serious genital tract injury and post-partum haemorrhage. This question addressed by this trial was whether induction of labour for suspected macrosomia could prevent shoulder dystocia and other maternal and perinatal morbidity, compared to expectant management.
This trial included 818 women who were suspected to have macrosomia on clinical examination, which was then confirmed with ultrasound between 36 and 38 weeks gestation. Women were randomized if the estimated weight of the fetus was more than the 95th percentile (3500 g at 36 weeks of gestation, 3700 g at 37 weeks, and 3900 g at 38 weeks). Those randomised to ‘induction’ had labour induced between 37+0 and 38+6. Those randomized to expectant management had their hospital’s ‘routine care’; awaiting spontaneous labour unless an indication for induction became apparent, such as preterm PROM or 41 weeks. The composite outcome comprised: significant shoulder dystocia (difficulty delivering the shoulders: required internal manoeuvres or ≥ 60 seconds head-to-body delivery interval), fracture of clavicle or long bone, brachial plexus injury, intracranial haemorrhage and death.
Results confirmed that those in the expectant management group were on average born 10.5 days later, weighing 287 g more. The primary composite outcome was three times lower in the induction group, occurring in 2% of babies that were induced compared to 6% of those managed expectantly (RR 0.32: 0.15-0.71). Shoulder dystocia was also halved, occurring in 4% of the induction group compared to 8% of those managed expectantly. The spontaneous vaginal delivery rate was significantly higher in those induced. The caesarean section rate did not differ between the two groups (28% in the induction group; 32% in the expectant management group).
Overall this study concluded that IOL for suspected macrosomia reduces shoulder dystocia and increases spontaneous vaginal delivery rates without increasing caesarean section rate. This study is a very important contribution to the literature, since previous studies addressing this question had largely used retrospective datasets. Nevertheless, there are some caveats that should be kept in mind when considering translating these findings into clinical practice. This trial recruited 822 women across 19 sites over 7 years. This means each centre recruited only 6 patients/ year on average, which can limit applicability of the findings to all pregnant women. This slow recruitment may have contributed to the trial being stopped prior to reaching its prospectively determined sample size. In addition, over 50% of the women were multiparous, a group at much lower risk of caesarean section following induction of labour. Finally, the unblinded nature of this study means that the clinicians were aware of suspected macrosomia. Clinicians are much more likely to undertake caesarean section when the baby is known to be macrosomic. This may have influenced decisions regarding mode of delivery, particularly those with more advanced gestation in the expectant management group.