Warmer Nights During Pregnancy Linked to Higher Autism Risk

Study finds association between higher nighttime temperatures and increased autism diagnoses in children

Published on Feb. 13, 2026

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A new study led by researchers at Tulane University has found that higher nighttime temperatures during pregnancy may be associated with a higher risk of autism diagnosis in children. The study examined nearly 295,000 mother-child pairs in Southern California from 2001-2014 and discovered that exposure to warmer overnight temperatures, especially during early and late pregnancy, was linked to a 15% and 13% increased risk of autism, respectively.

Why it matters

As global temperatures rise, this study is the first to examine how temperature can impact fetal neurodevelopment. The findings add to growing research on how environmental factors like air pollution and wildfire smoke may influence prenatal development. The results indicate a need to consider heat exposure around the clock, not just daytime heat, and how it may affect pregnant women and their developing babies.

The details

The study compared weekly outdoor temperature estimates at residential addresses with autism outcomes in children. The association held even after accounting for factors like neighborhood conditions, vegetation, and air pollution, though the researchers were unable to factor in access to air conditioning. Researchers did not find the same link with daytime temperatures, potentially because people spend more time away from home during the day. They suggest higher nighttime temperatures could disrupt sleep for pregnant mothers, which has been previously linked to neurocognitive delays in children.

  • The study examined mother-child pairs in Southern California from 2001-2014.
  • Exposure to warmer overnight temperatures during weeks 1-10 of pregnancy was associated with a 15% higher risk of autism.
  • Exposure during weeks 30-37 of pregnancy was associated with a 13% higher risk of autism.

The players

Tulane University

The university where the lead researchers on this study are based.

Mostafijur Rahman

Assistant professor of environmental health sciences at the Celia Scott Weatherhead School of Public Health and Tropical Medicine at Tulane University.

David Luglio

A post-doctoral fellow with the Celia Scott Weatherhead School of Public Health and Tropical Medicine at Tulane University and the lead author of the study.

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What they’re saying

“Heat waves are becoming more frequent, and people may only think of the dangers of daytime heat exposure. These results indicate a strong association between high nighttime temperatures during pregnancy and autism risk in children and show that we need to think about exposure to heat around the clock.”

— Mostafijur Rahman, Assistant professor of environmental health sciences (Tulane University)

“A key takeaway is that we identified specific windows when a mother and her developing child can be most affected by exposures to higher nighttime temperatures. This is critical and hopefully can help mothers prepare accordingly.”

— David Luglio, Post-doctoral fellow (Tulane University)

What’s next

Researchers say more studies are needed to understand the biological mechanisms behind how higher nighttime temperatures during pregnancy may impact fetal neurodevelopment and lead to increased autism diagnoses.

The takeaway

This study is the first to examine the link between rising global temperatures, especially at night, and autism risk in children. The findings underscore the need to consider heat exposure beyond just daytime hours and how it may affect pregnant women and their developing babies, especially as extreme heat events become more frequent.