[How long can we wait at full dilatation. A study of maternal and neonatal morbidity related to the duration of the second stage of labour in nulliparous women]. / Combien de temps peut-on attendre à dilatation complète? Analyse de la morbidité maternelle et foetale selon la durée de la seconde phase du travail chez la primipare.

OBJECTIVES: To determine the statistical association, in nulliparous patients, between maternal and fetal morbidity and the length of the second stage of labour. To precise whether a prolongation of this period of more than 2h may results in a dramatic increase of this morbidity. MATERIALS AND METHODS: Retrospective cohort study conducted in a level III referral centre between 1 April 2004 and 30 April 2005, including all nulliparous, term, cephalic, live singleton birth without fetal malformation in patients reaching the second stage of labour (n=1191). All deliveries were performed without restrictions in the length of the second stage of labour in the absence of fetal heart rate abnormalities. Maternal and neonatal morbidity were examined according to the duration of the second stage of labour with univariate analysis and after statistical adjustment with multivariate logistic regression for potential confounding variables. RESULTS: Global maternal morbidity ranged from 5.7% after 1h to 20.4% after more than 3h of full cervical dilatation. After a second stage duration of 2h, each additional completed hour resulted in a significant increase in global maternal morbidity (OR 1.78; IC 95% [1.59-1.97]), postpartum haemorrhage (OR 1.72; IC 95% [1.21-2.23]) and level three or four perineal lacerations (OR 1.24; IC 95% [1.7-1.41]). In the same time, caesarean section rate (OR 2.09; IC 95% [1.84-2.34]) and operative vaginal deliveries (OR 1.82; IC 95% [1.59-2.05]) increased significantly. Conversely, our study didn't demonstrate any significant association between neonatal morbidity and the length of the second stage of labour. CONCLUSION: Our study confirmed the association between the duration of the second stage of labour and the increase of maternal but not neonatal morbidity. Such an association, predominantly after 3h spend at full cervical dilatation, needs to be taken into account and, according to our experience, may justify caesarean section.