Maternal and fetal factors affecting success of antepartum external cephalic version.

We studied 172 patients who were considered for external cephalic version with tocolysis at term. Before a single attempt at version, a variety of maternal and fetal factors considered likely to affect success were coded for each patient. Maternal age, height, and Quetelet index did not affect success. However, successful version was more likely in parous women than in nulliparous women, and less likely with cornual than with other placentations. Amniotic fluid volume, fetal abdominal circumference, type of breech, and the specific nature of the maternal-fetal spatial relation were also important determinants of success. Fetal biparietal diameter, gestational age, and estimated fetal weight were not. All of these factors can be evaluated before attempting version and can be used when counseling candidates for version.