Cesarean section and operative vaginal delivery in low-risk primiparous women, Western Australia

OBJECTIVES. A major component of the increasing trend in cesarean sections in Western Australia is the rise in emergency cesarean sections in primiparous women. The aim of this study was to identify independent risk factors (particularly those known early in pregnancy) associated with operative delivery in low-risk primiparous women. METHODS. Retrospective multivariate logistic regression analyses of antenatal and perinatal data were conducted for all low-risk primiparous women entering labor spontaneously and giving birth in Western Australia in 1987 (n = 3641). RESULTS. Of the subjects, 58% had a spontaneous vaginal delivery, 8% had an emergency cesarean section, and 34% had an operative vaginal delivery. The significant independent risk factors for emergency cesarean section were older maternal age, shorter maternal height, heavier infant birthweight, and long labor. The risk factors for operative vaginal delivery were older maternal age, shorter maternal height, heavier infant birthweight, epidural anesthesia, labor/delivery complications, male infant, private patient status, and being married. CONCLUSIONS. This multivariate analysis confirms known risk factors for operative delivery in low-risk primiparous women and suggests that it may be possible to predict the likelihood of operative delivery for an individual woman by using knowledge of maternal age and height and assessment of infant birthweight.