The diagnostic values of concurrent nonstress testing, amniotic fluid measurement, and Doppler velocimetry in screening a general high-risk population

To determine the values of individual and combined biophysical fetal surveillance tests in a general high-risk population, we examined 1000 consecutive pregnancies complicated by either postdatism, hypertension, intrauterine growth retardation, or diabetes mellitus. Nonstress tests, amniotic fluid pocket measurements, and umbilical artery Doppler velocimetry were performed on each patient; each test was rated against gestational age-adjusted standards. Clinical end points included perinatal mortality, intrapartum fetal distress, 5-minute Apgar score <7, and neonatal acidosis in pregnancies without major anomalies or extreme prematurity (age at birth >32 weeks), delivered within 72 hours of final tests. Each testing method had specificity >90%. Sensitivities ranged from 69% (nonstress test) to 21% (Doppler velocimetry). Negative predictive values of each method exceeded 85%; positive predictive values ranged from 81% (nonstress test) to 42% (amniotic fluid measurements). The positive predictive value for any abnormal test was 54% and increased to 100% when all tests were abnormal; this latter condition occurred in only 2% of the total population. Amniotic fluid measurements or Doppler velocimetry, when compared with the nonstress test, appeared to be less powerful "stand-alone" screening tests. The performance of all tests in a single session confers little improvement in detection of fetal compromise if the nonstress test is normal; however, this approach may aid decision-making in the management of pregnancies when fetal maturity is not established.