OC01.03: Uterine artery vasodilation and its impact on maternal and perinatal outcomes in aspirin‐using pregnant women for preterm pre‐eclampsia prevention

To determine the effect of the change in the uterine artery pulsatility index (UtA-PI) between the first and second trimesters of pregnancy on the maternal and perinatal outcomes of pregnant women using aspirin due to the high risk of developing preterm pre-eclampsia (PE) at the Fetal Medicine Unit of the University of Chile Hospital between 2018-2020. This nested case-control study included pregnant women with ultrasound scans at 11-14 and 20-25 weeks. Cases (n = 43) were defined based on a risk of preterm PE > 1:100, aspirin users, and UtA-PI > 50th percentile. Controls (n = 408) were defined by a risk of Preterm PE < 1:1000 and a UtA-PI < 50th percentile. The dependent variable was the delta UtA-PI between the first and second trimesters. The independent variables were the development of preterm PE, gestational age at delivery, and newborn weight percentile. Statistical analyses were performed according to the type of variables. As expected, preterm PE was significantly more frequent in cases than in controls (27.9% vs 2.9%, p < 0.05). Interestingly, there was greater vasodilation of the uterine arteries in the cases group than in the controls, as expressed by the Delta UtA-PI (-0.92 vs -0.51, p < 0.05). Finally, the Delta UtA-PI was significantly lower in pregnant women who developed preterm PE despite using aspirin since 14 weeks. The odds ratio (OR) of the Delta UtA-PI for preterm PE was 11.8. This preliminary study demonstrates that pregnant women at high risk of preterm PE treated with aspirin have greater uterine artery vasodilation between the first and second trimesters of pregnancy than control pregnant women. Additionally, pregnant women who develop preterm PE despite taking aspirin have less uterine artery vasodilation than those who do not develop the disease. This finding suggests that aspirin may have an effect on the remodelling of the spiral arteries. However, to confirm these findings, a study with a larger number of patients is required.