Postpartum X-ray pelvimetry. Its use in calculating the fetal-pelvic index and predicting fetal-pelvic disproportion.
OBJECTIVE
To determine whether postpartum x-ray pelvimetry can be used to calculate the fetal-pelvic index (FPI) in future pregnancies.


METHODS
In stage I of the study, 10 gravid women, after 36 completed weeks' gestation, underwent x-ray pelvimetry before delivery. Pelvimetry was repeated within two days after delivery. Comparisons between antepartum and postpartum measurements were made using paired t tests and correlation coefficients. In stage II, 25 gravid women, after 36 completed weeks' gestation, underwent fetal ultrasound for biometry. X-ray pelvimetry was performed within two days after delivery. FPI was calculated for each pregnancy using antepartum fetal ultrasound and postpartum pelvimetry measurements. FPI calculations were correlated with the incidence of fetal-pelvic disproportion (FPD), as indicated by the requirement for cesarean section for arrest of active labor. Sensitivity, specificity and predictive value of FPI were assessed.


RESULTS
In stage I, mean anteroposterior and transverse diameters of the pelvic inlet, midpelvis and pelvic outlet did not differ significantly. In stage II, the sensitivity of FPI for detecting FPD was 100%, specificity 95%, positive predictive value 80%, and negative predictive value 100%.


CONCLUSIONS
Postpartum pelvimetry has the same association with FPD as antepartum pelvimetry. The strategy of using postpartum pelvimetry and antepartum fetal biometry to calculate FPI successfully identified 100% of the patients who ultimately required cesarean section for FPD, with a false positive rate of 5%. Pelvimetry performed postpartum in an index pregnancy may be used in future pregnancies, in combination with antepartum fetal ultrasound, to calculate FPI and predict the likelihood of FPD.
O'Brien
Karen
K
Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Women and Infants' Hospital, 101 Dudley Street, Providence, RI 02905, USA.
Rode
Martha
M
Macones
George
G
D000328:Adult; D001724:Birth Weight; D002508:Cephalometry / Q000379:methods*; D002585:Cesarean Section / Q000706:statistics & numerical data; D005189:False Positive Reactions; D005260:Female; D020073:Gravidity; D006801:Humans; D015994:Incidence; D007744:Obstetric Labor Complications / Q000175:diagnosis* / Q000453:epidemiology / Q000209:etiology / Q000628:therapy; D010387:Pelvimetry / Q000379:methods*; D011181:Postnatal Care / Q000379:methods*; D049590:Postpartum Period; D011237:Predictive Value of Tests; D011247:Pregnancy; D011263:Pregnancy Trimester, Third; D011295:Prenatal Care / Q000379:methods*; D011446:Prospective Studies; D016216:Ultrasonography, Prenatal / Q000379:methods*