Best Gestation Period in Nulliparous Women


Research into labour induction versus expectant management in low-risk nulliparous women has demonstrated that inducing labour at 39 weeks does not result in a lower occurrence of adverse perinatal outcomes. However, inducing labour at this time did result in a significantly lower rate of cesarean deliveries.

Historically, induced labour has been avoided in pregnant women 39 weeks 0 days and 40 weeks 6 days into their pregnancy. This has been due to the lack of evidence of perinatal benefit and concern about adverse perinatal outcomes resulting from induced labour. The evidence that does exist is mostly observational, not clinical. Such evidence has not demonstrated a higher risk of adverse outcomes with labour induction.

During the 2018 ARRIVE trial (A Randomized Trial of Induction Versus Expectant Management), a total of 3062 women were assigned to labour induction and 3044 were assigned to expectant management during childbirth. The former practice involves using mechanical or medical devices to start the process of childbirth. The latter practice involves simple observation of the women giving birth – no medication is given until necessary.

Perinatal death or serious perinatal complications arose in 4.3% of babies in the induction group and in 5.4% of the ‘watch and wait’ group. This is not a significant difference. The frequency of cesarean deliveries in the first group was 18.6% and 22.2% in the second group – a significant difference.

The women selected for the study were chosen based on a lack of pregnancy complications and a sound awareness of the time of their last menstrual period. Women who were in labour or who had premature rupture of membranes or vaginal bleeding were considered to be ineligible for the study.

The results of the study show that one cesarean delivery may be avoided for every 28 deliveries amongst low-risk nulliparous women who plan to undergo elective induction of labour at 39 weeks. Results contradict historic observational studies that have suggested labour induction is associated with an increased risk of adverse maternal and perinatal outcomes.

In summary, the study found that elective labour induction at 39 weeks of gestation did not result in a greater frequency of perinatal adverse outcomes than expectant management and resulted in fewer instances of cesarean delivery. Therefore, policies aimed at avoiding induced labour are unlikely to reduce the rate of cesarean delivery on a population level.

Contact Dr Nicole Stamatopoulos with any questions regarding your pregnancy and induced labour.