'Momnesia' pregnancy forgetfulness linked to brain circuit disruption

Momnesia, also known as mommy brain or pregnancy brain, refers to the forgetfulness and cognitive changes some women experience during pregnancy. Scientists have identified a disrupted brain circuit as the possible cause. Using lab mice with elevated estrogen levels similar to those during pregnancy, researchers found temporary memory impairment without mood changes.

The disruption occurs between the hypothalamus and hippocampus, two brain structures. High estrogen increased hypothalamus neuron activity, suppressing hippocampus activity and impairing memory. Momnesia usually occurs in late pregnancy and may continue postpartum but typically resolves after childbirth. The phenomenon affects short-term and long-term memory, including spatial, social, and verbal memory.

About 80% of pregnant women report these changes, though self-reported figures may not be entirely accurate. The findings suggest the issue is not a general decline in intelligence but rather a subtle, specific cognitive effect. In mice, the disruption was reversible by turning off the hypothalamus-to-hippocampus pathway. A study of 70 women found memory impairments during late pregnancy correlated with high estrogen levels, supporting the mechanism discovered in mice.