Spontaneous labour: when should the membranes be ruptured?

Sixty-eight patients (32 multigravidae, 36 primigravidae) with intact membranes admitted in early spontaneous labour were studied. Patients were randomly allocated to two groups: group I had an immediate amniotomy and group II were allowed to retain their membranes intact until full dilatation. Early amniotomy significantly shortened the length of labour and reduced the need for augmentation and instrumental delivery. There were no differences between the two groups in fetal outcome as measured by Apgar scores, umbilical arterial and venous blood pH, neonatal jaundice or admission to the special-care baby unit. Fetal heart-rate recordings obtained in group I by applying a fetal electrode after amniotomy were of superior quality to those obtained in group II by ultrasound and were more suitable for interpretation. 'Normal' and 'suspicious' tracings occurred equally in the two groups. Our results suggest some benefits from early amniotomy and no adverse effects on the fetus.