Objective: To determine if the addition of uterine artery (UA) Doppler pulsatility index (PI) at 18 and 22 weeks of gestation improves the predictive accuracy of low first trimester pregnancy associated plasma protein A (PAPP-A) in the detection of adverse obstetrical outcomes.
Methods: This was a prospective interventional study. All women undergoing first trimester combined screening (FTS) at a single center, with a low maternal serum PAPP-A level (<0.4 MoM), were included. Patients underwent bilateral UA Doppler assessments at 18 and 22 weeks of gestation. A positive test was defined as a mean PI > 1.45. Primary outcomes were obtained from chart review, and logistic regression analysis was used to compare outcomes with positive and negative tests. Positive and negative predictive value, specificity and sensitivity were calculated.
Results: Between January and October 2007, 5359 women completed FTS. Among the low PAPP-A group (n = 289), 18 week UA Doppler was a significant predictor of low birth weight (OR = 2.28, p = 0.04) while 22 week UA Doppler significantly predicted preterm birth (OR = 12.6, p = 0.001), small for gestational age (OR = 8.24, p = 0.001) and low birth weight (OR = 2.28, p = 0.04). Test characteristics suggested improved positive and negative predictive value for Doppler at 22 versus 18 weeks for these outcomes.
Conclusions: UA Doppler at 22 weeks is a useful adjunct in patients with low PAPP-A. However, a negative Doppler does not rule out all adverse outcomes and clinical judgment is advised in the management of these patients.