ArticlesInduction of labour versus expectant management for large-for-date fetuses: a randomised controlled trial
Introduction
Macrosomia is a risk factor for unfavourable delivery outcomes, including operative vaginal or caesarean delivery and shoulder dystocia.1, 2 Shoulder dystocia can cause neonatal morbidity, including fracture of the clavicle, brachial plexus injury, or asphyxia. Elective caesarean section can be done to avoid a vaginal delivery complicated by macrosomia. However, findings from a decision analysis3 suggested that the number of elective caesarean sections needed to avoid one permanent brachial plexus injury is quite high. This strategy is thus recommended only when fetal weight is estimated to exceed 4500 g for women with diabetes and 5000 g for those without diabetes.4
Another option would be to induce labour, which reduces the opportunity for continued fetal growth and, theoretically, decreases the risk of caesarean section for cephalopelvic disproportion, and reduces the risk of operative vaginal delivery, perineal trauma, and shoulder dystocia. Nonetheless, induction of labour can fail, which would make caesarean delivery necessary. Early-term (37–38 weeks) delivery, especially by elective caesarean section, might also increase the risk of mortality and morbidity of the neonate, including long-term development issues.5, 6
Several investigators have raised questions about induction of labour for macrosomic fetuses, especially because most observational studies have associated this strategy with an increased risk of caesarean delivery, with no significant decrease in shoulder dystocia.7 A systematic review,8 which included the few randomised trials published,9, 10 showed no difference in the risk of caesarean section between the labour induction and expectant management groups, but also no benefit of labour induction in prevention of neonatal trauma. The conclusions were limited by the relatively small sample size of the trials and by the inclusion of women, usually at 40 weeks of gestation or more, carrying a fetus with an estimated weight of more than 4000 g. Inclusion of these women is likely to restrict the benefit of induction of labour, because this intervention at that stage of gestation leads to very small differences between induced labour and expectant management groups, in both mean gestational age at birth and birthweight.
We assessed the risks and benefits of induction of labour compared with expectant management in women with large-for-date fetuses. We postulated that induction of labour would prevent shoulder dystocia and other neonatal and maternal morbidity associated with macrosomia, with no major changes in the risk of caesarean section.
Section snippets
Study design and participants
We did this multicentre, randomised controlled trial in 19 tertiary-care university hospitals in France, Switzerland, and Belgium. Recruitment started on Oct 1, 2002, in four hospitals and was extended to France in 2005, which added 15 more hospitals. Recruitment ended on Jan 1, 2009.
Eligible women had a singleton macrosomic fetus in cephalic presentation and no contraindications to planned vaginal delivery. We identified the women in two stages, between 36 weeks and 38 weeks of gestation,
Results
The figure shows the trial profile. We randomly assigned 822 women to the induction of labour group (n=409) or the expectant management group (n=413). Four (1%) women were lost to follow-up before delivery, leaving 818 women in the final analysis. Labour was induced in 366 (89%) women in the induction group and 116 (28%) women in the expectant management group (figure). Baseline characteristics were similar between groups (table 1). Mean birthweight was 3831 g (324) in the induction group and
Discussion
Our findings show that induction of labour for large-for-date fetuses significantly reduces the risks of shoulder dystocia and bone fracture, and increases the likelihood of spontaneous vaginal delivery. We recorded no brachial plexus injuries, intracranial haemorrhages, or perinatal deaths, nor did we detect differences between the groups for markers of asphyxia at birth.
Our results differ from those of a systematic review,7 which reported an increased risk of caesarean delivery with no
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