[Does rupture of membranes have an impact on the fetal heart rate during spontaneous labor?]

Evaluate the influence of rupture of membranes (spontaneous or artificial) on fetal heart rate. Secondary objectives were to compare spontaneous and artificial ruptures and to investigate the risk factors associated with the occurrence of abnormalities of fetal heart rate (FHR).

This is a monocentric retrospective study (Lille, France) from January to March 2018. All low-risk pregnancies with cephalic presentation, spontaneous labor, gestational age more than 37 weeks of amenorrhea, singleton pregnancy, absence of maternal or fetal pathology were included. The elements sought were the occurrence of bradycardia, tachycardia, decelerations (early, late, typical variable, atypical variable, prolonged) and abnormal variability. FHR was analyzed one hour before and one hour after rupture. The groups with and without abnormalities of FHR were compared according to the type of rupture.

Two hundred and thirty-three patients were included. A total of 44.54% (n=129, P<0.001) showed abnormalities of FHR after rupture of membranes. In the fetal heart rate time study after the rupture event, prolonged decelerations were more frequent in the first quarter hour compared to the second quarter hour. There was significantly more risk of abnormalities of fetal heart rate if the fetal heart rate before the rupture of membranes was already pathological, as well as if the time between rupture and delivery was short. The type of rupture, artificial or spontaneous, was not a risk factor.

The rupture of membranes increased the occurrence of abnormalities of FHR. However, there is no more deleterious impact of one type of rupture than the other.