External cephalic version with tocolysis: factors associated with success.

Data were collected prospectively on factors that might affect the success or failure of external cephalic version, using a protocol including fetal monitoring, ultrasound, tocolysis, and external version after 37 weeks' gestation. Patients were accepted into the protocol whether or not risk factors for failure were present. Sixty-seven patients were admitted to the study and 40 (60%) underwent successful version. Using chi 2 analysis, we found that failure of external version was significantly associated with obesity, descent of the breech into the pelvis, decreased fluid, and fetal back positioned posteriorly. Thirteen women were in active labor; this had no effect on the success rate providing that descent had not occurred. Two factors, descent of the breech into the pelvis and posterior position of the fetal back, had an independent effect on success after controlling for other variables.