The effect of gestational age and placental location on the prediction of pre-eclampsia by uterine artery Doppler velocimetry in low-risk nulliparouswomen

Objective To assess how placental position and gestational age ran influenc e the value of a diastolic notch of the uterine arteries as a screening tes t for pre-eclampsia. In a low-risk population of healthy nulliparous women. Methods Color Doppler ultrasound was used to examine both uterine arteries in 654 healthy nulliparas at 4-week intervals between 20 and 32 weeks. The only criterion for an abnormal result was the presence of an early diastoli c notch. In each subject the placental position was also recorded. The majo r end points were pre-eclampsia and pre-eclampsia requiring delivery before the 34th week. Results Ninety-eight women (15%) had abnormal flow velocity waveforms at th eir first visit. Twenty-one out of 654 women developed ere-eclampsia (3.2%) . The sensitivity of the test became lower as gestational age advanced and ranged from 81% at 20 weeks, to 71.4% at 32 weeks. In contrast, the specifi city and positive predictive value increased significantly. Eleven out of 1 2 women who delivered before 34 weeks had abnormal waveforms at the 24th we ek. In women with a full lateral placenta, the predictive value of the test was extremely low, especially in cases with unilateral notches. Conclusion Pre-eclampsia can be more accurately predicted if, along with th e presence of a notch, both gestational age and placental position ale take n into account. At week 24 the test maintains a high sensitivity (76.1%), b ut also has an improved specificity (95.1%) and positive predictive value ( 34%), which allow the clinician to intervene with a potential preventive tr eatment.