Could Aspirin Treatment Modify the Assessment of the Uterine Arteries?

Objective:  To analyze whether acetylsalicylic (ASA) intake modifies the mean uterine arteries pulsatility index (UtA-PI) at the 2 or 3 trimester in a cohort of pregnant women with abnormal mean UtA-PI at between 11 and 14 weeks of gestation.

Methods:  This is a retrospective cohort study. Singleton pregnancies with abnormal mean UtA-PI at between 11 and 14 weeks of gestation were studied. The participants were divided into 3 groups: 1) If the participant did not take ASA during pregnancy; 2) If the participant took ASA before 14 weeks of gestation; and 3) If the participant took ASA after 14 weeks of gestation. The mean UtA-PI was evaluated at the 2 and 3 trimesters, and it was considered to improve when it decreased below the 95 percentile. The prevalence ratio (PR) and the number needed to treat (NNT) were calculated.

Results:  A total of 72 participants with a mean UtA-PI > 95 percentile at the 1 trimester of gestation were evaluated. Out of the 18 participants who took ASA, 8 participants started it before 14 weeks of gestation and 10 after. A total of 33.3% of these participants had improved the mean UtA-PI at the 2 and 3 trimesters of gestation, although it was not statistically significant ( = 0.154). The prevalence ratio was 0.95 (95% confidence interval [CI]: 0.31-1.89), but between the 1 and 2 trimesters of gestation, the PR was 0.92 (95%CI: 0.21-0.99) and it was statistically significant.

Conclusion:  The present work demonstrates a modification of the mean UtA-PI in participants who took ASA compared with those who did not. It is important to check if ASA can modify the normal limits of uterine arteries because this could have an impact on surveillance.