Efficacy of the fetal-pelvic index in nulliparous women at high risk for fetal-pelvic disproportion.
OBJECTIVE
The null hypothesis of this study is that the fetal-pelvic index will not determine the presence or absence of fetal-pelvic disproportion in 137 nulliparous women at high risk for fetal-pelvic disproportion.


METHODS
This study was undertaken by comparing the blinded fetal-pelvic index values and two other methods of identifying fetal-pelvic disproportion, ultrasonography-derived estimated fetal weight greater than or equal to 4000 gm and Mengert's index, to delivery outcomes in 137 nulliparous women at high risk for fetal-pelvic disproportion.


RESULTS
After adequate labor trials, 55 of 73 patients who required operative intervention had a positive fetal-pelvic index (sensitivity = 75%). Seventeen of the 18 patients with a false-negative fetal-pelvic index value had persistent malpositions (15 occipitoposterior, 1 occipitotransverse, and 1 face presentation). Spontaneous vaginal deliveries occurred in 64 patients with 62 of them having a negative fetal-pelvic index (specificity 97%). The overall predictability of the fetal-pelvic index in this patient population was 85% and the positive predictability was 96%. However, neither ultrasonography-derived estimated fetal weight nor x-ray pelvimetry, when used alone, accurately detected the presence or absence of fetal-pelvic disproportion in nulliparous women at high risk for the condition.


CONCLUSIONS
The fetal-pelvic index is efficacious in determining the presence or absence of fetal-pelvic disproportion in nulliparous women at high risk for the condition.
Morgan
M A
MA
Department of Obstetrics and Gynecology, University of California, Irvine Medical Center, Orange 92668.
Thurnau
G R
GR
D001724:Birth Weight; D002585:Cesarean Section; D005260:Female; D006801:Humans; D007743:Labor, Obstetric; D007744:Obstetric Labor Complications / Q000000981:diagnostic imaging*; D010298:Parity; D010387:Pelvimetry / Q000379:methods* / Q000592:standards; D011247:Pregnancy; D012307:Risk Factors; D012680:Sensitivity and Specificity; D016216:Ultrasonography, Prenatal