First-trimester screening for preeclampsia: Impact of maternal parity on modeling and screening effectiveness

Objective: The impact of maternal parity on screening efficiency for preeclampsia (PE) has been poorly studied. Our objective was to investigate the effect of maternal parity on models for screening for PE in the first-trimester and their effectiveness.Study design: A secondary analysis of a prospective cohort study of women present between 11 and 14 weeks gestation. Maternal risk factors, uterine artery Doppler, mean arterial pressure (MAP) and serum markers including PAPP-A, ADAM12, PP13 in the first-trimester were used to create multi-parameter screening models for PE. The best models for screening in nulliparous versus parous women were developed using backward stepwise logistic regression approach. The area under the receiver operating characteristic curves (AUC) and the sensitivity for fixed false positive rates of 10% and 20%, respectively, were compared using non-parametric statistics.Results: Among 1177 women with complete outcome data (503 (42.7%) nulliparous and 674 (57.3%) multiparous), PE occurred in 102 (8.7%). There were significant differences in predicting variables in the final optimal models when stratified by parity; and screening performance also varied by parity. The AUC for the model for nulliparous women was 0.88(95% CI 0.80-0.95); and for multiparous was 0.84 (95% CI, 0.75-0.91). For fixed false positive rate of 10%, the sensitivity for predicting PE was 70% and 68% for nulliparous and multiparous, respectively. The screening performance for the models were however not statistically or clinically significantly different.Conclusion: We found significant differences in prediction model parameters between nulliparous and multiparous women, but these did not significantly impact screening performance for PE in the first-trimester.