Mommy Brain

Maternal Brain Chemistry

A woman's brain is primed to find maternal activities emotionally rewarding. Studies using functional magnetic resonance imaging (MRI) technology find that shortly after delivery, mothers exhibit increased brain activity in three regions known to create a powerful sense of reward or pleasure: the medial preoptic area (mPOA) found in front of the hypothalamus; the ventral tegmental area (VTA); and the nucleus accumbens (NA). It is generally understood that the mPOA initiates maternal behavior and that the VTA and NA provide the pleasurable emotional response. A mother needs only to gaze upon photos of her newborn to stimulate these brain regions.

Levels of oxytocin, endorphine, and prolactin increase substantially in the mother's brain, and function as hormones in the body and as neurotransmitters in the brain. Oxytocin stimulates uterine contractions and lactation, and diminishes stress by inhibiting the release of glucocorticoids. Endorphins cause a sense of well-being, and in combination with elevated oxytocin, lead to warm, relaxed social experiences between mother and child. These two hormonal changes set the foundation for developing powerful bonds of attachment. These effects may last longer than was previously expected. Women who breastfed their babies for eight or more weeks reported that they felt more relaxed, less tense, and more trusting even three to six months after they stopped. A third hormone, prolactin, causes milk ejection during lactation, but also has a strong behavioral effect. In animal studies, prolactin increases boldness and bravery even to the point where animal mothers will put their life at risk for the sake of their young.

Disruptive Changes

Not all mothers experience these powerful, adaptive, emotional changes, however. The first weeks following childbirth are also associated with an increase in vulnerability to mood disorders. Hormonal changes can become disregulated and lead to mild depression in up to 50 percent of mothers. Of those who experience the “baby blues,” 20 percent will go on to develop postpartum depression. Symptoms include sadness, anxiety, and anhedonia (a lack of pleasure or the capacity to experience it).

Studies suggest women who have gone through a major life stressor during pregnancy or soon following delivery may become highly sensitive to the rapid drop in progesterone during delivery. [Page 790]Progesterone increases during pregnancy and is necessary to sustain it. The metabolite of progesterone, called allopregnanolone, stimulates the release of GABA (a neurotransmitter that inhibits excitatory responses) in the amygdala (adjoining the temporal lobe of the brain and involved in emotions of fear and aggression), causing a decrease in anxiety.

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