Interpregnancy Stability of the First-Trimester Uterine Artery Pulsatility Index: A Within-Woman Comparison with PAPP-A and Free β-hCG in 864 Women

Background/Objectives: First-trimester screening combines a haemodynamic marker, the uterine artery pulsatility index (UtA-PI), with two serum markers, pregnancy-associated plasma protein A (PAPP-A) and free β-human chorionic gonadotropin (free β-hCG). For the serum markers, it is known that the value measured in one pregnancy correlates with the value measured in the same woman’s next pregnancy. For UtA-PI, only decreases in the mean value in second pregnancies have been reported. This study quantifies how much of a woman’s standardised UtA-PI persists from one pregnancy to the next and compares this persistence with that of the serum markers measured in the same woman.