New research has discovered an unexpected way pregnancy alters the brain—by changing a mother’s temperature preferences.

A study from the Baylor College of Medicine found that postpartum women prefer cooler environments due to brain changes that affect temperature regulation.

“We found the neurons in the preoptic area (POA) are changed in postpartum female mice,” paper author and professor of pediatrics Chunmei Wang told Newsweek.

“These neurons express estrogen receptor alpha (ERα) and can be excited by estrogen,” she said. “Previous reports showed that the majority of ERαPOA neurons can be activated by temperature increase, defined as warm-activated ERαPOA subpopulation.”

Using mice models, the researchers discovered that female mice developed a long-term preference for cooler temperatures after giving birth.

Even weeks after weaning their young, postpartum mice consistently chose cooler environments compared to their pre-pregnancy state. While they still avoided cooler temperatures, they lost their usual preference for warmth.

“In both humans and mice, body temperature increases during early pregnancy, drops to normal temperature during late pregnancy and then goes up again during lactation,” said Wang.

Pregnancy brings significant metabolic adaptations to support fetal growth but until now, little was known about how it affects body temperature regulation.”

To understand why this shift occurs, the researchers focused the POA brain region, which is responsible for sensing and regulating body temperature.

Their findings showed that postpartum females had a significant decrease in ERα-expressing neurons in the POA.

Further experiments revealed that when virgin female mice had their estrogen receptor alpha deleted in these neurons, they displayed the same temperature preference as postpartum mice—favoring cooler environments while avoiding warmth.

The study also uncovered that different ERαPOA neurons respond to warm and cold stimuli. In postpartum mice, the neurons that detect warmth had a reduced response, while the neurons that sense cold became more active.

Wang clarified the difference between two concepts about thermal regulation.

Thermal preferred temperature is the ambient temperature where you feel most comfortable. Below this temperature, you feel too cold, and above it, you feel too hot.

Thermoneutrality or thermal neutral zone is a range of temperatures where your body can maintain a stable core temperature with minimal effort.

“When environmental temperature is below this zone, your body need to initiate cold defense reactions like warmth seeking behavior, increase heat production through shivering, to prevent core body temperature drop,” Wang told Newsweek.

These findings might be relevant for understanding postpartum mood disorders like PPD, but there is no evidence yet, she clarified.

“It has been confirmed that higher environmental temperature impairs maternal behavior in mice,” Wang said.

“Thus, the preference to low temperature area should be beneficial for maternal care. Indeed, ERαPOA neurons have been reported to be essential for maternal care.”

More research is needed to understand how these neurons behave during late pregnancy and lactation, and how they affect mood changes and maternal care.

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Reference

Zhang, N., Yu, M., Zhao, Q., Feng, B., Deng, Y., Bean, J. C., Liu, Q., Eappen, B. P., He, Y., Conde, K. M., Liu, H., Yang, Y., Tu, L., Wang, M., Li, Y., Yin, N., Liu, H., Han, J., Threat, D. A., … Wang, C. (2025). Altered thermal preference by preoptic estrogen receptor alpha neurons in postpartum females. Molecular Metabolism, 93. https://doi.org/10.1016/j.molmet.2025.102108