Perinatal outcome after a prolonged second stage of labor.

It is commonly held that the second stage of labor should last no more than two hours because of an apparently increased risk of morbidity. The purpose of this investigation was to determine whether this commonly held notion is true in this era of close fetal monitoring and umbilical blood gas determination. Between May 1987 and October 1988, 50 (3.5%) of 1,432 uncomplicated term pregnancies ended in delivery after a second stage of labor lasting greater than 120 minutes. A prolonged second stage was associated more commonly with nulliparity, occiput posterior positioning, epidural anesthesia and a need for operative delivery but not birth weight greater than 4,000 g or a short umbilical cord. Infants born after a prolonged second stage did not have an increased incidence of umbilical artery pH less than 7.20 or of five-minute Apgar scores less than 7, nor did they need intensive care nursery admission. A prolonged second stage of labor appears not to impose an increased hazard on the fetus but does require close fetal monitoring and increases the possibility of operative delivery.