Aspirin mitigates preterm birth risk linked to heat exposure

Initiating low-dose aspirin early in pregnancy may reduce the risk of preterm birth associated with heat exposure among nulliparous women, according to a study.

Researchers conducted a secondary analysis of the Global Network ASPIRIN trial. The analysis included 11,558 nulliparous participants (mean age 20.9 years) between 6 and 13 weeks of gestation who delivered at ≥20 weeks of gestation. Of these, 5,787 were randomized to receive aspirin and 5,771 to receive placebo.

The main outcome of preterm birth was defined as delivery occurring between 20 and <37 weeks of gestation, with gestational age confirmed via ultrasonography. Preterm birth occurred in 11.6 percent of participants in the aspirin group vs 13.1 percent of those in the placebo group.  

The odds of preterm birth increased by 5 percent for each 1-°C increase in mean daily maximum shaded wet-bulb globe temperature across gestation (adjusted odds ratio [aOR], 1.05, 95 percent confidence interval [CI], 1.01–1.10). This association was observed in the placebo group (aOR, 1.07, 95 percent CI, 1.02–1.13) but not in the aspirin group (aOR, 1.03, 95 percent CI, 0.97–1.10).

In further analysis, the increased odds of preterm birth were seen between 17 and 19 weeks before delivery among participants whose daily maximum shaded wet-bulb globe temperature exceeded the site-specific 75th percentile vs the lowest 3 quartiles. However, this was not observed in the aspirin group.

Meanwhile, the association between heat exposure and perinatal mortality was observed in the aspirin group (aOR, 1.15, 95 percent CI, 1.05–1.26) but not in the placebo group (aOR, 1.03, 95 percent CI, 0.96–1.11).