Efficacy of the fetal-pelvic index in patients requiring labor induction.

The fetal-pelvic index is a recently described means of identifying the presence or absence of fetal-pelvic disproportion. In this follow-up study, the efficacy of the fetal-pelvic index was evaluated in 49 patients requiring labor induction and was compared with two other methods used to identify fetal-pelvic disproportion (Colcher-Sussman x-ray pelvimetry and ultrasound-derived estimated fetal weight). Twelve of 14 patients who required operative intervention also demonstrated a positive fetal-pelvic index (sensitivity = 86%). Spontaneous vaginal deliveries occurred in 35 patients, all of whom demonstrated negative fetal-pelvic index values (specificity = 100%). Overall the predictability of the fetal-pelvic index was 96%. In comparison, when used alone, neither x-ray pelvimetry nor ultrasound-derived estimated fetal weight accurately detected the presence or absence of fetal-pelvic disproportion in patients requiring labor induction.