Out of all the changes that happen during pregnancy—spreading feet, dwindling bladder, and hair-trigger emotions—the scariest part is when you become convinced that you’re losing your mind. For many women, pregnancy is a time when they feel spacey, disconnected, and forgetful. They forget where they parked their car, they lose things, and sometimes they can’t even find the right words to carry on a simple conversation.

Some people call it “pregnancy brain,” “mommy brain,” “pregnesia,” or “momnesia,” but it’s the unfortunate reality for many expectant mothers, who, for many reasons, just don’t feel like their former capable, confident selves. So not only does pregnancy irreparably change our figures and our social lives, but it hijacks our brains, too?

Babies on the Brain

Pregnancy does change a woman’s brain, in both temporary and permanent ways. Almost from the moment of conception, a woman’s brain begins to change and develop new circuitry in order to prepare her for motherhood. In the first few months of pregnancy, the brain changes how it processes sensory information, including how it reacts to olfactory signals. The brain becomes extremely sensitive to smells, in order to steer women away from eating foods that might harm the developing fetus. Once her body gets used to her new nasal hard-wiring, a woman’s brain keeps the fetus on her mind at all times, chemically bonding with the unborn child and leaving little room for any other thoughts, like where she put her keys or the last name of an important client. In these first few months, levels of the hormone progesterone rise to about one hundred times their pre-pregnancy levels. With the brain bathing in progesterone, it acts like a sedative, inducing an amnesiac haze.

The body also produces large amounts of stress hormones during pregnancy, including cortisol, and their effect is to make a woman vigilant about her health, her safety, and her surroundings, and leaving little room for thinking about day-to-day tasks. Pregnant women go through a well-documented nesting phase where they become fixated on their home, their living situation, and even may even reassess whether their partner is a capable provider. The parts of the brain that are usually responsible for focus and concentration become obsessed with protecting the baby. It may seem counterintuitive for a woman’s brain to protect the baby by making the woman spaced out, but the woman’s conscious and unconscious mind are so extra-vigilant about the baby that they don’t devote energy to much else.

“Mommy, I Shrunk Your Brain!”

Functional MRI scans have shown that not only do women’s brains undergo chemical changes, they also undergo physical changes. A 1996 report in New Scientist magazine found that women’s brains shrunk during the last trimester of pregnancy, and that problems with concentration, coordination, and memory could be related to the change. A similar study in the January 2002 American Journal of Neuroradiology found that women’s brain volume diminished by about 4 percent. Scientists are unsure of exactly why the size of the brain changes, but in The Female Brain, Dr. Louann Brizendine writes, “It’s not that a woman is losing brain cells … the mother’s brain shrinks because of changes in cellular metabolism required for restructuring brain circuits—getting ready to turn some one-lane highways into superhighways.” Even as some areas of the brain shrink, other areas, including the forebrain, which is responsible for problem solving and higher reasoning, expand and develop. The forebrain develops new communication conductors that enable mothers to protect their babies.

The brain begins to return to its normal size a few weeks before the baby is born, although it can take up to six months to regain its former size. But even though the brain returns to its pre-pregnant state, it retains its new and improved circuitry. Animal studies have shown that mothers have less fear, better memories, and are more efficient hunters and providers than females without children. Dr. Brizendine also says, “Mothers may have better spatial memory than females who haven’t given birth, and they may be more flexible, adaptive, and courageous.” These brain changes last a lifetime and are even present in the brains of adoptive mothers. Any kind of constant contact with a child is enough to trigger the development of the “mommy brain.”

Not Just in Your Head

Although many studies have found that women’s brains change size during pregnancy, some researchers still believe that “momnesia” is more of a psychological phenomenon than a physical one. They believe that the memory lapses and confusion are normal, and just chalked up to pregnancy as a convenient excuse. However, even the American Psychological Association says that anywhere from 50 to 80 percent of women experience some concentration and memory problems associated with pregnancy. It’s not just all in your head.

Pregnancy is often a time of limitations. Expectant women are encouraged to put down the cookie dough and watch their diet and to abstain from alcohol, seafood, litter-box changing, caffeine, and whatever else may be harmful to babies that week. It can alter a woman’s body forever, so pregnancy isn’t always viewed as a time of positive changes. However, the changes that pregnancy inflicts on the brain are long lasting and impossible to refute. For all the pain and discomfort of carrying a child, women are rewarded with fantastically flexible and nimble brains that could make them better problem-solvers. The “pregnancy brain” makes women more sensitive, more adaptable, and more nurturing. In short, “pregnancy brain” is what turns a woman into a mom.