Effect of low dose aspirin prophylaxis on severe prematurity

Abstract

In 2014, the USPSTF recommended the use of Low dose aspirin (LDA) as preventive medication in persons at high risk for preeclampsia (LeFevre ML et al. Ann Intern Med. 2014) . The recommendations were disseminated at our Institution in 2015. LDA prophylaxis, though recommended to reduce risk of preeclampsia, has subsequently been shown to reduce the risk of preterm birth (PTB) (Matthew K. Lancet 2020). We have evaluated the effect of recommendations for LDA prophylaxis on risk of severe prematurity (BW < 1500 gm) for the period prior to vs after 2015, when LDA prophylaxis was implemented at our Institution. Retrospective cohort study of all delivery data from 1/1/2011-12/31/2021 compiled in a convenience dataset through the National Perinatal Information Center. The percent of deliveries with BW of 500-750 gm, 750-1500 gm, and the sum of the two were calculated. Chi-square for trend was used to compare trends 2011-2015 vs 2016-2021. Rates of PTD 500-1500 gm were significantly lower in the second than the first time period (0.9% or 180/19420 vs 1.3% or 241/18,684, P=0.001; OR=0.72, 95% CI 0.59-0.87). Chi-square for trend showed significantly increasing trend in the first period (P=0.036) and significantly decreasing trends in the second period (P=0.036) (Figure 1). The reduction was predominantly due to a decrease in rates of BW 750-1500 gm (P=0.034) than BW 500-750 gm (P=0.496). During the study period there were no significant changes in recommendations for progesterone prophylaxis in women with history of preterm delivery or short cervix; moreover, the trends in rates of cerclage were not significant in the 1st (P=0.68) or 2nd (P=0.69) period. Introduction of LDA prophylaxis has led to a significant decrease in rates of PTB < 1500 gm.