Inducing labour at 41 weeks of pregnancy leads to a small reduction in birth complications compared with expectant management (a "wait and see" approach) until 42 weeks in low risk women, finds a clinical trial published by The BMJ today.
However, the absolute risk of serious problems was low in both groups - and a linked editorial says the results are not sufficiently conclusive to change current practice, which is in line with the authors' interpretation.
Late term pregnancy (at or beyond 42 weeks) affects about 15% of women and is associated with increased problems at birth (known as adverse perinatal outcomes), including death.
Some studies suggest that inducing labour from 41 weeks onwards improves outcomes for both mother and baby, but these studies were different regarding their measures, protocols and time frames of comparison and so the results need to be interpreted with caution.
Yet despite these concerns, induction at 41 weeks is now an accepted policy in many countries throughout the world.
So researchers of the INDEX-team led by senior researcher Esteriek de Miranda at the Amsterdam UMC-University of Amsterdam, set out to compare induction of labour at 41 weeks with expectant management until 42 weeks in low risk pregnancies.
The trial included 1800 women (mainly white and younger than 35 years) with an uncomplicated pregnancy recruited from 123 midwifery practices and 45 hospitals in the Netherlands.
Women were randomised to either induction at 41 weeks or expectant management until 42 weeks with subsequent induction if necessary.
Adverse perinatal outcomes were assessed using a combined measure of the newborn's health (including perinatal death, Apgar score of less than 7 five minutes after birth, and admission to an intensive care baby unit). Other outcomes included type of delivery and mother's health just after giving birth.
Fifteen women (1.7%) in the induction group had an adverse perinatal outcome compared with 28 (3.1%) in the expectant management group - an absolute risk difference of 1.4% in favour of the induction group.
Eleven (1.2%) infants in the induction group and 23 (2.6%) in the expectant management group had an Apgar score of less than 7 out of 10 at five minutes.
No infants in the induction group and three (0.3%) in the expectant management group had an Apgar score of less than 4 out of 10 at five minutes.
One fetal death (0.1%) occurred in the induction group and two (0.2%) in the expectant management group. No neonatal deaths (deaths in the first 28 days of life) occurred.
Three (0.3%) infants in the induction group versus 8 (0.9%) in the expectant management group were admitted to an intensive care baby unit.
No significant differences in the mother's health or in caesarean section rates were found between groups.
The researchers point to some potential limitations, but say in this large trial induction of labour at 41 weeks resulted in less overall adverse perinatal outcome than a policy of expectant management until 42 weeks, although the absolute risk of severe adverse outcome was low in both groups.
As with every intervention in the natural birth process, the decision to induce labour must be made with caution, as the expected benefits should outweigh possible adverse effects for both mother and child, they add.
As such, they say their results "should be used to inform women approaching 41 weeks of pregnancy, so they can weigh the respective outcomes and decide whether to be induced at 41 weeks or to continue pregnancy until 42 weeks."
In a linked editorial, Professor Sara Kenyon at the University of Birmingham and colleagues welcome this new trial, but say the results "are not sufficiently conclusive to change current practice."
They point out that, if the Apgar scores are excluded, "the remaining data suggest little to choose between the two management options." And they warn that increasing induction rates (35% of women giving birth for the first time are currently induced in the UK) "may also impact negatively on women's birth experience."