Middle cerebral to umbilical artery Doppler ratio in post-date pregnancies.

OBJECTIVE

To determine which antepartum test is the best predictor of post-date-related adverse outcome among the amniotic fluid index (AFI), nonstress test (NST), biophysical profile, or middle cerebral artery to umbilical artery Doppler ratio.

METHODS

Pregnant women of 41 or more weeks' gestation with singleton fetuses and vertex presentations underwent antepartum testing twice a week. Pulsed Doppler ultrasound was used to obtain the flow velocity waveforms from the umbilical and middle cerebral arteries. Adverse post-date-related outcome was defined as the occurrence of meconium aspiration syndrome, cesarean delivery for fetal distress, or fetal acidosis. The predictive values of an AFI equal to or less than 5 cm, a biophysical profile score equal to or greater than 6, a nonreactive NST, and a middle cerebral artery to umbilical artery ratio less than 1.05 in identifying adverse outcome were compared.

RESULTS

Forty-nine women met the inclusion criteria; ten (20.4%) had an adverse outcome. A middle cerebral artery to umbilical artery ratio of less than 1.05 was found to be the best predictor of adverse outcome, with a sensitivity of 80%, specificity of 95%, positive predictive value of 80%, and negative predictive value of 95%. The other three diagnostic tests had sensitivities equal to or less than 40%. The middle cerebral artery to umbilical artery ratio was also a better discriminator of adverse outcome than either the umbilical artery systolic-diastolic (S/D) ratio or the middle cerebral artery S/D ratio.

CONCLUSION

Although the sample size of our study was small, the results suggest that a middle cerebral artery to umbilical artery ratio of less than 1.05 is an accurate method of predicting post-date-related adverse outcome.