Doppler flow velocimetry of the umbilical artery, uteroplacental arteries and fetal middle cerebral artery in prolonged pregnancy

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Abstract
A total of 153 pregnant women, of at least 287 days' menstrual age, were studied in a prospectively designed cross‐sectional trial. In addition to the non‐stress test, contraction stress test, sonographic estimate of amniotic fluid and grade of placental maturation, Doppler measurements of the resistance index (RI) were taken in the umbilical artery, the uteroplacental arteries in the region of placental implantation and the fetal middle cerebral artery. Data were analyzed with regard to asphyxia and otherwise complicated fetal outcome. Furthermore, a possible relationship between grade of placental maturation, Doppler flow velocity waveforms and fetal outcome was investigated. Doppler resistance indices in the umbilical artery, uteroplacental arteries in the region of placental implantation and fetal middle cerebral artery did not change significantly with increasing gestation from 41 to 43 weeks. The grade of placental maturation on ultrasound examination was not related to fetal outcome or Doppler indices in the first two vessels. In all vessels examined in this study, the majority of Doppler measurements in pregnancies with subsequent asphyxia or otherwise complicated fetal outcome were within the 95% prediction interval for patients with normal fetal outcome. None of the patients showed absent diastolic flow in the umbilical artery. With the use of a cut‐off value of RI = 0.62 in the umbilical artery, asphyxia could be predicted with 37% sensitivity and 75% specificity. Oligohydramnios and antepartum cardiotocography predicted asphyxia with 16% and 8% sensitivity and 95% and 96% specificity, respectively. Sensitivity for prediction of otherwise complicated fetal outcome by umbilical artery Doppler was only 7%. We conclude that vascular resistance in the umbilical artery, uteroplacental arteries in the region of placental implantation and the middle cerebral artery does not change abruptly, when gestation exceeds 287 days. Ultrasonographic grading of placental maturation has no use in post‐term pregnancies. Doppler investigations of the umbilical artery had somewhat better sensitivity in the prediction of asphyxia when compared to ultrasound diagnosis of oligohydramnios or antepartum cardiotocography. However, Doppler showed only modest specificity compared to the other methods and probably has few advantages compared to the traditional methods of fetal surveillance. Copyright © 1995 International Society of Ultrasound in Obstetrics and Gynecology

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