A comparison of Doppler flow velocity waveforms, amniotic fluid columns, and the nonstress test as a means of monitoring post-dates pregnancies.

Five hundred thirty-four pregnancies exceeding 294 days were monitored by weekly sonographic estimations of amniotic fluid columns, daily maternal recordings of fetal movements, and thrice-weekly nonstress tests. In addition, each woman received twice-weekly studies of the uteroplacental and umbilical circulations by means of Doppler ultrasound. There were no fetal deaths in the study. Of the individual methods of fetal surveillance, absence of end-diastolic frequencies in the umbilical artery was the most sensitive, predicting 91% of fetuses who developed fetal distress in the first stage. Combining the test with sonographic estimation of amniotic fluid columns improved the prediction to 100%, with only a minimal fall in the specificity. These results strongly suggest that a combination of umbilical artery Doppler waveforms and amniotic fluid determinations is an adequate method of monitoring the post-dates pregnancy.