How long is a ‘full term’ pregnancy and how ‘late’ can a pregnancy go? Chapter: Week 36
With careful medical monitoring you can go up to 10 days after your own individual calculated due date. This could be 41-and-a-half weeks or 42 weeks depending on your hospital’s policy and your history and health. As explained in Up the Duff, there are important exceptions to this. Multiple births (twins or triplets) can be considered full term at 37 weeks, and women of African or South Asian heritage (India, Pakistan, Sri Lanka, Afghanistan and Bangladesh) can be naturally ‘full term’ at 38 or 39 rather than 40 weeks. After week 40 they have a greater statistical risk of stillbirth, and of fetal distress. This must be taken into account when making a decision about when to induce labour, so talk to your pregnancy-care team if you have any of these backgrounds in your ethnic heritage.
For most other women, obstetricians and midwives don’t like to leave it past 41-and-a-half weeks. If you go beyond 10 days overdue the doctor will probably induce the birth as the placenta might start to deteriorate.
There’s more on pregnancy duration, induction and labour in the book Up the Duff: The Real Guide to Pregnancy.