Doppler ultrasound of the umbilical artery has been subjected to more extensive assessment with randomized controlled trials than has any previous test of fetal health. Williams and colleagues (2003) randomized 1360 high-risk women to either nons tress testing or Doppler velocimetry. hey found a significantly higher incidence of cesarean delivery for fetal distress in the nonstress test group compared with that for those tested with Doppler velocimetry-8.7 versus 4.6 percent, respectively. One interpretation of this finding is that the nonstress test more frequently identiied fetuses in jeopardy. Conversely, Gonzalez and associates (2007) found that abnormal umbilical artery Doppler indings in a cohort of growth-restricted fetuses were the best predictors of perinatal outcomes.
he utility of umbilical artery Doppler velocimetry was reviewed by the American College of Obstetricians and Gynecologists (2016). They concluded that no beneit has been demonstrated other than in pregnancies with suspected fetal-growth restriction. Similarly, velocimetry has not proved valuable as a screening test for fetal compromise in the general obstetrical population.
Various other fetal-maternal Doppler indices have been studied, including the fetal middle cerebral artery and ductus venosus and the uterine arteries. The American College of Obstetricians and Gynecologists (2016) concluded that Doppler investigations of other blood vessels besides the umbilical artery have not been shown to improve perinatal outcome.
As discussed, at this time, Doppler velocimetry interrogation of the middle cerebral artery (MCA) to detect fetal compromise is not recommended. Still, the technology has received particular attention because of observations that the hypoxic fetus attempts brain sparing by reducing cerebrovascular impedance and thus increasing blood flow. Such brain sparing in growthrestricted fetuses has been documented to undergo reversal (Konje, 2001). Investigators reported that 8 of 17 fetuses with this reversal died. Ott and coworkers (1998) randomized 665 women undergoing modified biophysical proile evaluation to either the profile alone or combined with middle cerebral and umbilical artery velocity low assessment. Pregnancy outcomes between these two study groups did not difer significantly.
Middle cerebral artery Doppler velocimetry has proven valuable to detect severe fetal anemia in 165 fetuses with D-antigen alloimmunization. Oepkes and colleagues (2006) prospectively compared serial amniocentesis for measurement of bilirubin levels with Doppler measurement of peak systolic velocity in the middle cerebral artery. These investigators concluded that Doppler could safely replace amniocentesis in the management of alloimmunized pregnancies. And as discussed in Chapter 15 (p. 303), this technique has been reported to be useul for detection and management of fetal anemia of any cause (Moise, 2008).
Doppler ultrasound has also been used to assess the fetal venous circulation. Bilardo and colleagues (2004) prospectively studied umbilical artery and ductus venosus Doppler velocimetry in 70 growth-restricted fetuses at 26 to 33 weeks' gestation. hey concluded that ductus venosus velocimetry was the best predictor of perinatal outcome. Importantly, negative or reversed low in the ductus venosus was a late finding because these fetuses had already sustained irreversible multiorgan damage due to hypoxemia. Also, gestational age at delivery was a major determinant of perinatal outcome independent of ductus venosus flow. Specifically, 36 percent of growth-restricted fetuses delivered between 26 and 29 weeks' gestation succumbed compared with only 5 percent delivered from 30 to 33 weeks.