This report presents results of a comparison perineal muscle function between antepartum and postpartum measurements in a cohort of women with different perineal conditions after childbirth. Data were obtained by using prospective electromyographic perineometry measurements to objectively determine perineal muscle function before and after delivery in 102 women. In addition, 24 nulliparous, non-pregnant women were studied to determine the effect of pregnancy on perineal muscle function. Pregnancy is associated with a decrease in perineal muscle strength and endurance compared with the postpartum state. The degree to which women improved or did not improve perineal muscle function after birth was related to perineal trauma at delivery. After controlling for parity, maternal age, birthweight, smoking status, and antepartum scores, the order of best to worst performance was cesarean birth, intact perineum, first-degree perineal injury, second- or third-degree perineal injury, and episiotomy. Pre- and post-delivery scores were compared for each woman and analyzed according to perineal outcome. Although all other perineal outcome groups increased muscle function by 6 months postpartum, women with an episiotomy had a mean net loss of perineal muscle performance after birth. These observations do not support the use of episiotomy for the purpose of preserving perineal muscle function.