Cerebral, umbilical, and uterine resistance using Doppler velocimetry in postterm pregnancy.

The purpose of this study is to assess alterations in vascular resistance as measured by Doppler ultrasound in the postterm fetus. Forty-five postterm patients (greater than or equal to 287 days gestation by "good" dates) underwent Doppler velocimetry and calculation of systolic to diastolic (S/D) ratios of the umbilical, internal carotid, and uterine artery waveforms within 7 days of delivery. Patients were divided into two groups. Group 1 consisted of 26 patients with normal antepartum fetal surveillance that included reactive nonstress test and an amniotic fluid index (using the four-quadrant technique) equal to or greater than 5 cm. Group 2 consisted of 19 patients with antepartum compromise on the antepartum fetal surveillance tests. There was significantly greater (p less than .05) morbidity in group 2 compared to group 1 as judged by cesarean section for fetal distress (47% vs 15%), meconium at delivery (53% vs 4%), and 5-minute Apgar score less than 7 (30% vs 4%). There were no significant differences in the umbilical and uterine artery S/D ratios in the two groups, although patients in group 2 had significantly lower cerebral S/D ratios (3.6 +/- .5) compared to group 1 (4.4 +/- 0.4) (p less than .05). The ratio of cerebral to placental (umbilical) resistance in group 2 was significantly lower (1.1 +/- .3) compared to group 1 (1.8 +/- .3) (p less than .05). There was a low incidence of abnormal umbilical (greater than 3) and uterine (greater than 2.6) S/D ratios in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)