Preterm birth trends in the United States post aspirin recommendation guidelines

To evaluate changes in preterm birth (PTB) rates in the U.S. following the United States Preventive Services Task Force (USPSTF) aspirin recommendation guidelines.

A retrospective cohort study was conducted using the US Natality database. The pre-aspirin (pre-ASA) group included births from 2010-2014, while the post-aspirin (post-ASA) group included births from 2016-2021. Births from 2015, the guideline publication year, were excluded. Outcomes were overall PTB rates (<37 weeks) and early PTB rates (<34 weeks). Univariable and multivariable analyses were performed. Projected trends based on 2010-2014 data were compared to observed trends post-guideline implementation to assess differences.

The pre-ASA group included 12.1 million births, and the post-ASA group included 17.6 million. Adjusted analyses showed lower PTB rates in the post-ASA group: <37 weeks (8.4 % vs 8.8 %; aOR 0.940 [0.937-0.944]) and <34 weeks (2.3 % vs 2.4 %; aOR 0.92 [0.910-0.923]). However, observed post-ASA trends closely followed projected trends until 2021, when PTB rates exceeded projections.

Although adjusted analyses suggest modest reductions in PTB following USPSTF aspirin guidelines, observed trends did not show a clear reduction following aspirin implementation.