Spectral Doppler index mapping of the umbilicoplacental circulation and pregnancy outcome.
OBJECTIVE: To determine the value of Doppler measurements obtained by a new multigate Doppler modality, the spectral Doppler index mapping (SDIM) technique, to predict adverse outcome among pregnant women with normal conventional umbilical artery (UA) Doppler indices. DESIGN: A cross-sectional prospective cohort study. SUBJECTS: 183 women with well-dated singleton pregnancies who underwent prenatal ultrasound examination between 18 and 40 weeks of gestation were included in the study. At the time of the initial Doppler examination, all patients had normal UA and uterine artery Doppler indices, size appropriate for gestational age, no evidence of fetal anomalies or fetal distress. METHODS: SDIM data included the distribution curves of the pulsatility indices (PI) as well as the mean of the PI detected in the placenta and in the umbilical cord. The mean PI values were also calculated using conventional spectral Doppler sonography. Logistic regression analysis was used to control for gestational age while assessing various Doppler variables in predicting outcome. RESULTS: Adverse outcomes occurred in 26.6% of the pregnancies. In pregnancies with adverse outcome, the umbilicoplacental PI gradient was significantly lower (0.10 vs. 0.28, p < 0.003), the maximum intraplacental PI value was higher (1.28 vs. 1.16, p = 0.031), and there was a greater proportion with skewed UA distribution curves. Using forward stepwise logistic regression to compare the predictive value of the conventional Doppler ultrasound with SDIM, we found that the most accurate predictors of adverse outcome were the maximum intraplacental PI value (p < 0.028), skewed distributions (p = 0.002) and the gradient between the umbilical and intraplacental PI distributions (p = 0.006). CONCLUSIONS: Our results suggest that the SDIM system may enhance the ability of Doppler technology to predict obstetrical outcomes in patients with normal UA Doppler indices.