Baschat and coworkers (2007) studied 604 growth-restricted fetuses using umbilical artery, middle cerebral artery, and ductus venosus Doppler velocimetry and reached similar conclusions. Speciically, absent or reversed flow in the ductus venosus was associated with profound generalized fetal metabolic collapse. hey too reported that gestational age was a powerful cofactor in ultimate perinatal outcome for growth-restricted fetuses delivered before 30 weeks. Put another way, by the time severely abnormal low is seen in the ductus venosus, it is too late because the fetus is already near death. Conversely, earlier delivery puts the fetus at risk for death due to preterm delivery. Ghidini (2007) concluded that these reports do not support routine use of ductus venosus Doppler in the monitoring of growth-restricted fetuses and recommended further study.
Vascular resistance in the uterine circulation normally decreases in the irst half of pregnancy due to invasion of maternal uterine vessels by trophoblastic tissue (Chap. 5, p. 92). This process can be detected using Doppler flow velocimetry, and uterine artery Doppler may be most helpful in assessing pregnancies at high risk of utero placental insuiciency (Abramowicz, 2008). Persistence or development of high-resistance patterns has been linked to various pregnancy complications (Lees, 2001; Yu, 2005). In a study of 30,519 unselected British women, Smith and colleagues (2007) assessed uterine artery velocimetry at 22 to 24 weeks' gestation. The risk of fetal death before 32 weeks, when associated with abruption, preeclampsia, or fetal-growth restriction, was significantly linked to high-resistance flow. This has led to suggestions for continued research of uterine artery Doppler velocimetry as a screening tool to detect pregnancies at risk for stillbirth (Reddy, 2008). Sciscione and Hayes (2009) reviewed the use of uterine artery Doppler flow studies in obstetrical practice. Because standards for the study technique and criteria for an abnormal test are lacking, they noted that uterine artery Doppler studies should not be considered standard practice in either low-or high-risk populations.
Antenatal forecasts of fetal health have clearly been the focus of intense interest, and several themes emerge. First, despite a continuous evolution of testing options, the precision or eicacy of any given method is limited. Second, the wide range of normal biological fetal variation makes interpretation of test results challenging. Last, despite the invention of increasingly complex testing methods, abnormal results are seldom reliable, prompting many clinicians to use antenatal testing to forecast fetal welness rather than ilness.
Platt and coworkers (1987) reviewed the eicacy of antenatal testing between 1971 and 1985 at Los Angeles County Hospital. During this 15-year period, more than 200,000 pregnancies were managed, and nearly 17,000 of these women underwent antepartum testing of various types. Fetal surveillance rose from < 1 percent of pregnancies in the early 1970s to 15 percent in the mid-1980s. hese authors concluded that such testing was clearly beneicial because the fetal death rate was signiicantly less in the tested high-risk pregnancies compared with the rate in those not tested. he study, however, did not consider other innovations incorporated into practice during those 15 years. Preliminary results from Ghana suggest that nonstress testing may be beneicial in low-resource countries (Lawrence, 2016). In an observational study of 316 pregnancies complicated by gestational hypertension, women undergoing nons tress testing had a nonsignificant decreased risk for stillbirth compared with those not tested-3.6 versus 9.2 percent, respectively.