Among low-risk, nulliparous women, inducing a pregnancy at 39 weeks will not only be at least as safe as letting nature run its course but it will reduce the risk of having a Caesarean, according to US research.
According to the randomised trial involving over 6000 women, those who were assigned to ‘expectant management’ ended up having a median gestational age of 40 weeks exactly, not a huge difference from the median gestational age of the induction group which was 39.3 weeks.
However, the main aim of the study was to determine if induction at 39 weeks resulted in more adverse perinatal outcomes including conditions such as perinatal death, need for respiratory support, Apgars of less than three at five minutes, intracranial haemorrhage and the like.
This potential association has been the concern which has dictated what is currently common obstetric practice.
“When gestation is between 39 weeks 0 days and 40 weeks 6 days, common practice has been to avoid elective labour induction because of a lack of evidence of perinatal benefit and concern about a higher frequency of Caesarean delivery and other possible adverse maternal outcomes, particularly among nulliparous women”, the study authors said in the new England Journal of Medicine.
What they found in their study however, was that these adverse perinatal outcomes occurred in only 4.3% of the babies born in the induction group and in 5.4% of those born to mothers who went into labour naturally. It appears the relative risk was reduced by 20%. And even though the induction group tended to have longer labours they had quicker recovery times and shorter hospital stays.
In terms of maternal outcomes, induction at 39 weeks was associated with a significant reduction in the risk of both Caesarean section and hypertensive disorders of pregnancies. The researchers estimated one Caesarean would be avoided for every 28 low-risk, first-time mothers induced at 39 weeks.
The study authors suggest that these findings have the capacity to change practice, or at the very least, provide evidence to relook at current obstetric practice policies.
“These results suggest that policies aimed at the avoidance of elective labour induction among low-risk nulliparous women at 39 weeks of gestation are unlikely to reduce the rate of Caesarean delivery on a population level”, they concluded.
NEJM 2018; 379:513-23