[Prolonged pregnancy: when should surveillance be started and what should be the frequency?]

To determine when surveillance should be started in prolonged pregnancy and what would be the more appropriate frequency for it.

Systematic searches of Medline and the Cochrane Library were performed.

Fetal mortality diminishes from 37 weeks of gestation to a nadir of one death for 1000 births at 40(+0) weeks. It increases thereafter up to three deaths for 1000 births at 43(+0) weeks. Perinatal mortality rates show same pattern and is estimated to be of two and four to six deaths for 1000 births at 41(+0) and 43(+0) weeks, respectively. However, current available data does not allow for the determination of a gestational age cut-off associated with major increase of perinatal mortality and on which surveillance of prolonged pregnancy should be genuinely started. French epidemiological data from 2003 indicate that although 52.5% of pregnant women have reached 40(+0) weeks only 20,7% and 1% have reaches 41(+0) and 42(+0) weeks, respectively. Intrauterine fetal growth associated with prolonged pregnancy increases perinatal mortality. In most randomized trials having compared labour induction with expectant management, fetal surveillance was started at 41(+0) weeks.

Due to the increased risk of perinatal mortality, it seems appropriate that fetal surveillance is started at 41(+0) weeks (expert opinion). This implies a rational organization of care to support surveillance of 20% of pregnant women. The frequency of this monitoring consisting of at least twice-weekly cadiotocography and ultrasound estimation of amniotic fluid (expert opinion).