Efficacy of the fetal-pelvic index for delivery of neonates weighing 4000 grams or greater: a preliminary report.

The fetal-pelvic index was recently introduced as an accurate method of prospectively identifying the presence or absence of fetal-pelvic disproportion. In that report the ability to detect fetal-pelvic disproportion in patients with macrosomic fetuses was not specifically addressed. The objective of this study is to compare the efficacy of three methods used to identify the presence or absence of fetal-pelvic disproportion (the fetal-pelvic index, Colcher-Sussman x-ray pelvimetry, and estimated fetal weight greater than or equal to 4000 gm) in patients delivered of neonates weighing greater than or equal to 4000 gm after an adequate trial of labor (N = 34). Of the 18 patients requiring operative intervention, all but one had a positive fetal-pelvic index value (sensitivity = 94%). Of the 16 patients in whom vaginal deliveries were spontaneous, all but one had a negative value (specificity = 94%). On the basis of these data, the fetal-pelvic index is an accurate method of predicting the presence or absence of fetal-pelvic disproportion in patients delivered of neonates weighing greater than or equal to 4000 gm.