In women with late-term but otherwise low-risk, singleton pregnancies, labour induction at 41 weeks can decrease the risk of stillbirth and is preferred over expectant management. Additionally, in contrast to previous evidence, the Swedish Post-term Induction Study data suggest that no major harms are associated with labour induction. As women exceed term, they should be counselled on the risks of expectant management and offered induction of labour no later than at 41 weeks.BMJ 2019 Nov 20;367:l6131. doi: 10.1136/bmj.l6131 LINK
The average pregnancy lasts about 40 weeks from the start of a woman’s last menstrual period, but only about 5% of women deliver at exactly 40 weeks.1 While any delivery between 37 and 42 weeks is within normal range, adverse perinatal outcomes, including stillbirth and maternal complications, gradually increase past 40 gestational weeks and are significantly increased post-term (>42 weeks). Induction of labour may mitigate these adverse outcomes.
The latest Cochrane review (2018)2 highlighted evidence in favour of induction, but the question of when exactly to advise induction was left unresolved. While current guidelines in the UK3 and USA4 recommend induction of labour no later than 42 weeks, several studies suggest that the risk of adverse perinatal outcomes already increases significantly at 41 weeks. There is a paucity of data addressing induction between 41 and 42 weeks: only two of 30 studies included in the Cochrane review address this time frame.5 6 The Swedish Post-term Induction Study (SWEPIS) sought to clarify whether induction at 41 weeks results in a better outcome than expectant management (with labour induction at 42 weeks if necessary).