Low-dose aspirin may reduce heat-related preterm birth

What the study found: Low-dose aspirin started early in pregnancy may reduce the association between heat exposure and preterm birth among nulliparous pregnant people. The study also reported that the association between heat and perinatal mortality was seen only among those receiving aspirin.

Why the authors say this matters: The authors conclude that low-dose aspirin may help mitigate the effects of heat exposure on preterm birth, and they say the increasing global prevalence of heat stress warrants broader testing of its efficacy and its safety with respect to perinatal mortality.

What the researchers tested: This was a secondary analysis of the ASPIRIN randomized, double-blinded, placebo-controlled clinical trial. It included 11,558 nulliparous participants enrolled at 6 to 13 weeks' gestation in sites in the Democratic Republic of Congo, Zambia, Kenya, Guatemala, Pakistan, and India, and compared low-dose aspirin with placebo while examining site-specific daily maximum humid heat across pregnancy.

What worked and what didn't: Overall, each 1 °C increase in mean daily maximum shaded wet-bulb globe temperature across gestation was linked to higher odds of preterm birth. In stratified analyses, this increased risk was seen among placebo recipients but not among aspirin recipients, and distributed lag models found increased odds of preterm birth 17 to 19 weeks before delivery among those exposed to heat above the site-specific 75th percentile, again not among aspirin recipients. In contrast, the heat–perinatal mortality association was observed only among aspirin recipients.

What to keep in mind: This is a secondary analysis, so the findings are based on data from a prior trial rather than a study designed specifically for heat exposure. The abstract does not describe other limitations beyond the authors' call to test efficacy more broadly and assess safety regarding perinatal mortality.

Key points

• The study involved 11,558 nulliparous pregnant participants in six countries.
• Each 1 °C increase in average daily maximum shaded wet-bulb globe temperature across pregnancy was linked to a 5% increase in the odds of preterm birth.
• The heat-related increase in preterm birth odds was seen among placebo recipients but not among aspirin recipients.
• Heat exposure was associated with perinatal mortality only among those receiving aspirin.
• The authors say broader testing of aspirin's efficacy and safety is warranted.