A pregnancy is considered ''prolonged'' from 41 weeks of gestation. Prolonged Pregnancies
(PP) are associated with increased maternal morbidity: emergency caesarean, 3rd and 4th
degree perineal lesions and postpartum haemorrhage. Foetuses are at increased risk of
oligohydramnios, meconium-staining and Fetal Heart Rate (FHR) anomalies. Around 15% of all
pregnancies are prolonged.
A Cochrane review on induction of labour showed that a policy of labour induction at or
beyond 41 weeks was associated with significantly fewer perinatal deaths. Thus the French
College of Obstetricians and Gynaecologists stated, "induction of labour can be proposed to
patients between 41+0 and 41+6 weeks of gestation". In cases where labour is induced and
cervix is unfavourable, cervical ripening is advised. Methods of cervical ripening include
pharmacological (prostaglandins) and mechanical (Foley catheter or trans-cervical double
balloon) methods. Those two methods were compared in the PROBAAT trial among women with term
pregnancies (beyond 37+0). The rates of caesarean section with these two strategies were
identical, however uterine hyper stimulation with FHR anomalies occurred less when cervical
ripening was mechanical.
Considering pharmacological cervical ripening is associated with more uterine hyper
stimulation and more FHR anomalies, it may not be the most appropriate in cases of fragile
foetuses that include cases of prolonged pregnancies. Considering prolonged pregnancies are
associated with a risk of FHR anomalies and that cervical ripening with a pharmacological
method is another factor which increases this risk: women with prolonged pregnancies could
benefit from a more "gentle" cervical ripening.
At present, no particular method is recommended in cases of cervical ripening and prolonged
pregnancies. We hypothesise that, in cases of prolonged pregnancies, mechanical cervical
ripening, with less uterine hyperstimulation and fewer FHR anomalies, could be more
appropriate and could reduce the rate of caesarean section for suspicion of fetal distress.