B24. Overdue and postterm pregnancy

Overdue pregnancy refers to a pregnancy which has passed week 41+0 (day 287). Postterm pregnancy refers to pregnancy which has passed week 42+0 (day 294).

Postterm pregnancy is associated with several complications, due to the excessive foetal growth or due to placental insufficiency (as the placenta is unable to support the postterm foetus). Complications include oligohydramnios, intrauterine growth restriction, macrosomia, and meconium aspiration. There’s also a higher perinatal mortality.

Etiology

Risk factors for postterm pregnancy:

• Previous postterm pregnancy
• Nullipara
• Male foetuses
• Maternal obesity

Management

To prevent the complications of postterm pregnancy, pregnant women who reach week 41+0 are either frequently monitored from then on (every 2 – 3 days) followed by intervention (induction or C-section) if monitoring shows a worrying foetal status, or they’re admitted for labour induction (see topic B23). Stripping of the membranes is often performed to hasten labour.

In any case, no pregnancy should be allowed to reach week 43. If delivery hasn’t been induced yet, it usually is at week 42.