Risk factors for forceps delivery in nulliparous patients

OBJECTIVE: To identify risk factors for forceps delivery during first pregnancy. MATERIALS AND METHODS: A retrospective case-control study was carried out in a tertiary maternity ward between January 2001 and December 2003. A total of 582 nulliparous women, with full-term (>37 weeks gestation), singleton, cephalic pregnancies, who delivered by the vaginal route with or without instrumental assistance were evaluated. RESULTS: The strongest risk factors for forceps delivery were birth weight greater than 4000 g (OR: 6.5; 95% CI: 1.6, 26.9), the occiput posterior position of the fetal head (OR: 5.8; 95% CI: 2.5, 13.8), and epidural analgesia (OR: 7.7; 95% CI: 4.1, 14.7). Other significant risk factors for forceps delivery were age over 35 years (OR: 2.4; 95% CI: 1.1, 5.1), induction of labor (OR: 2.1; 95% CI: 1.4, 3.1), first stage of labor longer than 420 min (OR: 2.3, 95% CI: 1.3,4.2), and a prolonged second stage of labor (OR: 1.6, 95% CI: 1.1, 2.4). CONCLUSION: Age over 35 years and induction of labor are risk factors for forceps delivery at admission. Epidural use, fetal head in occiput posterior position, and birth weight >4000 g are strong intrapartum risk factors for instrumental delivery in nulliparous women.