Going past your due date?
It is common for pregnant women to go beyond their due date and only about five per cent of babies arrive on the day itself. Going post term is more common in first pregnancies. Most babies tend to arrive between 37 weeks and 41 weeks of gestation, usually within a week either side of their due date. Twins and triplets often arrive early.
During your pregnancy your preferences around birth and when you would like to deliver will be covered in depth. In low risk pregnancies you will be offered induction of labour at or just prior to your due date. You will also be given the option of going up to 10 days over.
In those opting to wait, an ultrasound is performed in the rooms at 41 weeks and fetal heart monitoring will be conducted to check the well-being of your baby. There is a significant increase in complications from the start of the 42nd week therefore induction of labour is offered again in the 41st week if you are yet to labour. Alternatively, for those not wishing to have an induction regular fetal monitoring will be arranged.
Why offer induction at term?
In the last few years new evidence has arisen about the when the ‘safest’ time for low risk women to deliver is at or after your due date. A number of large studies (e.g. ARRIVE) have pointed towards the safest course being induction of labour at 39-40 weeks resulting in a lower rate of caesarean and stillbirth. Understandably this has caused a lot of controversy.
The reality is that patients can be safely managed in a variety of ways, it’s important that you know all the facts and can make a properly informed decision.
What are the facts?
Evidence now suggests that in low risk women delivery just prior to or at term (39-40+0 weeks) reduces the risk of the death of a baby by about 2/3rds. That said the overall rate of still birth is very low. At 39 weeks it is 0.14 babies per 1000, at 40+0 it is 0.33 babies per 1000 and at 41+0 it is 0.80 babies per 1000. To put that in perspective one Danish study showed 754 inductions would have to be performed to prevent one perinatal death.
What effect does routine induction have upon other important outcomes for low risk women at term?
- Caesarean section: likely small reduction in the rate of caesareans
- Pre-eclampsia: a small but significant reduction in rate in the development of pre-eclampsia
- Pain: in one large trial there was a reported reduction in pain levels though epidural use was not measured (the evidence is unclear)
- Instrumental delivery: no significant difference
What are the downsides?
The major downside of induction is that it requires more intervention. On average women spend more time in hospital, require more interventions during the labour (e.g. monitoring and use of oxytocin) and potentially have reduced mobility in labour.
This above discussion points do not readily apply to women with additional risk factors in their pregnancy.
