Influence of in utero fetal death on perineal tears in vaginal deliveries.

The aim of this work was to evaluate and compare the incidence of perineal tears and Obstetrical anal sphincter injuries (OASIS) after vaginal delivery following a in utero fetal death (IUFD) compared with those with a live-birth. We conducted a single-center, retrospective cohort study using a database of all women who underwent a spontaneous vaginal delivery in the level III maternity ward. Exclusion criteria were breech presentation, cesarean section birth, instrumental delivery, multiple pregnancy, delivery before 24 + 6 weeks of gestation (WG) and termination of pregnancy for medical reasons. Women from the database were divided into two groups: an "in utero fetal death" (IUFD) group and a control group. Women were included in the IUFD group if they had a spontaneous vaginal delivery following a fetal demise after 24 + 6 WG in cephalic presentation between January 2006 and June 2020. Women in the "control" group were selected from the same database and were included if they underwent a spontaneous vaginal delivery of a live fetus in cephalic presentation, after 24 + 6 WG, during the same period. Each woman in the "IUFD" group was matched to two women (ratio 1:2) in the control group for parity, maternal age, body mass index, gestation and birth weight. The primary outcome was the presence of a sutured or unsutured perineal tear. During the study period, 31,208 patients delivered at a level III maternity hospital. Among them, 215 and 430 women were included in the IUFD group and the control group respectively. The two groups were comparable for all demographic and clinical characteristics except for an epidural analgesia (92% versus 70% in the control group, p < 0.01) and labor induction (86% versus 17% in the control group, p < 0.01). The incidence of any perineal tears was 13% (28/15) in the IUFD group versus 16% (70/430) in the control group. Relative risk of any perineal tears was non significative (RR = 0.8 IC95% [0.5-1.2]). The incidence of first-degree perineal tears was 10% in the IUFD group and 11% in the control group. The incidence of second-degree perineal tears was 18% in the IUFD group and 28% in the control group. Relative risk of first-degree perineal tears (RR = 0.88 95% CI [0.5-1.4]) and second-degree tears (RR = 0.51 95% CI [0.2-1.4]) were non significative. No obstetrical anal sphincter injury was found in either group. Vaginal delivery following a fetal demise did not appear to be either a risk factor or a protective factor for perineal tears. But there as a trend toward a lower incidence of second degree perineal tears in this context.