The fetal-pelvic index has minimal utility in predicting fetal-pelvic disproportion.
OBJECTIVE
Our purpose was to evaluate the fetal-pelvic index in our patient population and to determine whether it would be predictive of route of delivery.


METHODS
One hundred seventy-six patients with a previous history or clinical findings in the current pregnancy suggestive of fetal-pelvic disproportion participated in this Human Investigation Committee-approved study. All underwent fetal ultrasonographic examinations and modified digital radiography before labor. Fetal head and abdominal circumferences and maternal inlet and midpelvic circumferences were determined, and the fetal-pelvic index was calculated.


RESULTS
Ninety-one patients fulfilled all aspects of the study, including rigorous criteria pertaining to labor management. Thirty of these patients underwent cesarean delivery and 61 were delivered vaginally. The fetal-pelvic index value for the vaginal delivery group was -5.4 +/- 5.3, as opposed to -2.4 +/- 5.8 in the cesarean delivery group (P <.02). Notwithstanding this difference, the fetal-pelvic index had a low overall ability to predict fetal-pelvic disproportion (0.65) and had associated sensitivity and specificity of 0.27 and 0.84, respectively. Predictive thresholds other than zero were tested, but optimal predictive ability, at a fetal-pelvic index cutoff of 2, was only 70% (sensitivity 0.20, specificity 0.95).


CONCLUSIONS
In our patient population the fetal-pelvic index was only moderately predictive of fetal-pelvic disproportion. Factors other than those assessed by the fetal-pelvic index are probably important in determining the route of delivery. Further studies are indicated.
Ferguson
J E
JE
Departments of Obstetrics and Gynecology, Division of Radiological Physics, University of Virginia, Charlottesville, Virginia, USA.
Newberry
Y G
YG
DeAngelis
G A
GA
Finnerty
J J
JJ
Agarwal
S
S
Turkheimer
E
E
D000328:Adult; D000767:Anesthesia, Epidural; D001724:Birth Weight; D002585:Cesarean Section; D036861:Delivery, Obstetric / Q000379:methods*; D005260:Female; D005544:Forecasting; D006801:Humans; D007751:Labor, Induced; D010387:Pelvimetry; D011237:Predictive Value of Tests; D011247:Pregnancy; D011856:Radiographic Image Enhancement; D012680:Sensitivity and Specificity; D016216:Ultrasonography, Prenatal