1057 Pregnancies treated with prophylactic low dose aspirin: a dose dependent comparison of obstetric outcomes

Abstract

Low dose aspirin has been known as a potential treatment for prevention of the development of preeclampsia in high risk pregnancies since the 1980s. Since that time, multiple studies have confirmed this benefit as well as the reduction in rates of premature birth and low birth weight. As such, the United States Preventive Services Task Force (USPSTF) and American College of Obstetrics and Gynecology (ACOG) have published criteria outlining the pregnancies that most benefit from prophylactic low dose aspirin administration. However, there is no absolute recommendation as to the dosage of daily aspirin to be administered. We sought to determine if there is a dose dependent relationship for low dose aspirin prophylaxis and pregnancy outcomes. This was a retrospective cohort analysis of 231 pregnancies treated with prophylactic low dose aspirin in Kansas City between July 2016 and December 2019. Patients who did not receive prenatal care or deliver at our facility were excluded. We stratified patients by dose (81mg vs 162mg). Our outcomes of interest were gestational age at delivery and birthweight percentiles. Variables were compared using Student’s T-test. We found that the mean gestational age at delivery was later in the 81mg group than the 162mg group (37.84 +/- 2.16 weeks vs 36.55 +/- 4.74 weeks, p = 0.008) but birth weight percentiles were similar between groups (71.97% +/- 29.12 vs 58.41% +/- 29.66, p=0.606). The percentage of low birthweight infants were 8.2% (n=8) and 12.9% (n=20) in the 81mg and 162mg groups respectively, which are not statistically different from the general population. There was no difference in composite adverse neonatal events between groups. In this cohort of women treated with prophylactic low dose aspirin, increasing aspirin dose did not extend pregnancy duration or reduce the risk of low birthweight.