Pregnancy induces marked changes in the female body to prepare for birth, lactation, and the responsibilities of motherhood. A growing body of evidence suggests pregnancy also changes the female brain. A recent study in mice shows that estrogen and progesterone alter galanin-producing neurons in the brain, switching on maternal behavior before offspring arrive.

Researchers analyzed the effects of various pregnancy-related hormones on the brain activity of pregnant mice. Then they blocked the activity of the hormones and assessed the animals' behavior.

They found that estrogen dampened the baseline activity of galanin-expressing neurons in the hypothalamus while increasing their responsiveness. Progesterone reshaped the neurons' connections by driving more synapse formation. Blocking the two hormones' influence in pregnant mice prevented the emergence of maternal behavior, even after giving birth.

Galanin is a neurohormone and neurotransmitter produced in the central nervous system, particularly the hypothalamus. It plays versatile physiological roles in the neuroendocrine axis, such as regulating food intake and insulin levels and driving maternal and fetal weight gain during pregnancy.

These findings suggest that female hormones alter the brain during pregnancy, inducing maternal behaviors and ultimately influencing offspring survival. Learn how maternal health influences offspring health in this clip featuring Dr. Elisa Eppel.

• Read study abstract.