Effect of Parity on First-Trimester Uterine Artery Doppler Indices and Their Predictive Value for Pregnancy Complications

Aim: To investigate the relationship between parity and first-trimester uterine artery Doppler indices and determine their predictive value for pregnancy complications. Methods: In 679 singleton pregnancies (388 parous and 291 nulliparous) attending for routine care at 11-14 weeks of gestation, we recorded maternal characteristics, medical and obstetric history, the presence of protodiastolic notching and measured uterine artery resistance index (RI). Results: Parous women had a lower prevalence of bilateral notches (64 vs. 77.6%; p = 0.0002), median level of RI did not show any significant difference. In parous cases complicated with pregnancy-induced hypertension (PIH) (0.78 vs. 0.70; p = 0.0003) or miscarriage (0.86 vs. 0.71; p = 0.0003) mean levels of RI were significantly higher than in the nulliparous cases. By using mean RI we could predict the cases with PIH (area under curve (AUC) 0.63; p = 0.012), early PIH (AUC 0.84; p < 0.0001) and miscarriage (AUC 0.87; p < 0.0001) in the group of parous women. Conclusion: Parity has a significant effect on uterine artery Doppler findings in the first trimester of pregnancy. In the group of parous women the mean level of RI had a higher predictive value for miscarriage, early PIH and PIH.