The Pregnant Brain: How Mothers Think Differently.

Illustration by Lotta Nieminen

With 80 percent of women experiencing some form of impaired cognitive function during pregnancy, it's no surprise the idea of "pregnancy brain" has taken hold. But a recent paper suggests that the memory loss, stress, and general fuzzy-headedness of the prenatal period may actually have a crucial role in getting women ready to be mothers.

Since the 1940s, doctors have suspected that the hormonal bath of pregnancy helps prepare women for the demands of motherhood. But while there's plenty known about how hormones affect the teenage and the menopausal brains, the pregnant brain is poorly understood and little studied in humans. "Given that the vast majority of women give birth to at least one child, it's surprising to me that we don't know more about the maternal brain," says Laura M. Glynn, a professor of psychology at Chapman University.

Recent research has mostly been done on pregnant rodents, with studies finding that the hormone rush of pregnancy improved spatial skills (leading to better and quicker foraging for food) and multitasking, as well as increased boldness and decreased anxiety. These rats enjoyed the positive effects of having been pregnant throughout their lifetimes, long after their pups grew up.

Now scientists are attempting to apply the animal findings to people. In a new paper with Curt A. Sandman of the University of California–Irvine, Glynn argues for the existence of "maternal programming," a process by which the pregnant woman's hormone-soaked brain prepares for the challenges of parenthood. As it turns out, some of the worst parts about pregnancy—vague but nagging cognitive and memory lapses that are often dismissed as imaginary or just stress—may actually be side effects of the mental shifts that happen as a woman becomes a mother. In other words, you may be losing your memory at the same time you're gaining new capacities to bond with and care for an infant. Glynn says, "While there may be some less-than-ideal effects of this remodeling ... these are some really important processes."

Looking ahead, Glynn and her fellow researchers hope to study the effect of prenatal hormones on a wider array of cognitive functions, including multitasking; the possible benefits of past pregnancies on the aging female brain; and other little annoyances of pregnancy, such as sleep deprivation, that may have evolutionary functions. Glynn says her research reassures pregnant women that not only are the drawbacks of pregnancy not imaginary, they also serve a function: "I think people take some comfort [from our findings] and they don't feel like a crazy person."