This leaflet explores what happens in terms of health, well-being and induction of labour when your pregnancy goes beyond 42 weeks.

Calculating your due date and the definition of `prolonged pregnancy`

The length of a pregnancy is thought to be around 280 days, or 40 weeks. The estimated date for your baby`s birth (EDD) is calculated from the first day of your last menstrual period but some women will have their babies early while some women go on beyond their due date. It is not known why some pregnancies last longer, but there is some evidence that duration of pregnancy may be affected by hereditary (genetic) and racial factors, and that seasonal variations and shift work may also have an effect. There is also some evidence that prolonged pregnancy is more common if you are expecting a boy. In addition, some rare birth (congenital) abnormalities have been associated with prolonged pregnancy, because they interfere with the body`s natural mechanisms that encourage labour to start.

If your pregnancy goes beyond 42 weeks (294 days), this is then called a `post-term` or `prolonged` pregnancy.

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