You need to be aware that labour may start at any time. This is one of its 'indefinite' features, so you should always be ready to take appropriate action. Despite much advancement of maternal and fetal health sciences, so far nobody knows exactly:
- When is labour going to start?
That is why even the normal onset of labour is anticipated in a wide range of weeks (at Health Post level 37–40 weeks is considered the normal 'window'; at hospital level, it can be at 37–42 weeks with close follow up using ultrasound scanning). Although it is good to calculate the expected date of delivery as 40 weeks from the mother's last normal menstrual period (LNMP), if she knows the date (many mothers do not), tell her that she is probably not going to deliver on the expected date. Only about 2% of deliveries occur on the expected date even among women who know their LNMP date exactly. The other major indefinite features of labour are:
- What initiates/stimulates labour to begin? Is it factors in the fetus, the mother or both?
- Why do some women develop preterm labour?
- Why do unpredicted labour abnormalities occur?
We have to leave these questions unanswered, and focus on the normal labour occurring at term.