Mom Brain Explained

Forgetfulness and fatigue are common for new moms and pregnant women.

Medically reviewed in November 2020

If you’ve ever been pregnant or spent time around expectant or new moms, you may have noticed increased lapses in memory, fatigue, absentmindedness or a tendency towards distraction. Misplaced keys, forgotten appointments or nodding off in the middle of the day are all common for pregnant women and new moms. It’s such a frequent phenomenon that it even has a name—mom brain. But what is mom brain and what causes it?

The answer isn’t simple. It turns out there are many factors that impact a woman’s mental focus before and after giving birth. We spoke with Lisa Kimura, MBA and Executive Director of Healthy Moms Healthy Babies Coalition of Hawaii, and Rachel Ebert, LCSW (owner of Sunshine Therapy) and 2020Mom Speaking Ambassador who provides therapy for pregnant women and new moms, to learn more.

What is mom brain?
Mom brain, also known as mommy brain, pregnancy brain and baby brain, is a blanket term used to describe changes in cognition for pregnant women and new moms. Whatever you call it, women have long complained about forgetfulness and problems concentrating around having kids. In one of the first studies to look at the phenomenon from 1991, 64 percent of surveyed first-time moms reported cognitive changes during pregnancy, in a questionnaire administered three to five days after delivery. A secondary survey from the same study given to a mixture of pregnant and postpartum women showed that 82 percent reported cognitive changes in pregnancy, which included short-term memory loss, absentmindedness and difficulty concentrating.

Science backs up these self-reported observations. Multiple studies have shown that pregnant women perform worse than nonpregnant women in certain memory tasks. Notably, pregnant women have difficulty with verbal recall and short-term memory, but not recognition. Most, but not all studies have found these changes in pregnant women, but the exact deficits in memory and cognition varied a bit from study to study. Generally, a pregnant woman might recognize a car but have a hard time coming up with the type or model, even if it was well-known to her. Pregnant women also aren’t going to suddenly forget how to do regular tasks like driving a car, but they may forget street names.

The phenomenon of mom brain may be well documented, but it’s still not fully understood. It’s likely several elements that combine to create a mental fog during a major life experience for many women. While it’s not clear-cut, here are some of the things that are thought to cause mom brain.

Sleep deprivation becomes a way of life
Newborns need a lot of sleep—14 to 17 hours a day to be precise—but those hours of sleep often aren’t grouped together in a long stretch. Their need for regular feedings means most new parents aren’t getting their own recommended 7 to 9 hours of rest a night.

Kimura describes this period well: “Especially with the newborn parents, you're sleep deprived, you're thinking about things you've never thought about, and you can't even remember the last time you showered.”

Even before a baby is born, pregnant women often have difficulties with sleep, especially towards the end of pregnancy. This is a problem, as pregnant women may need a few more hours of sleep than the 7 to 9 hours recommended for most adults. The frequent need to urinate, physical discomfort, heartburn, stress, restless legs, vivid dreams and even possible sleep apnea can all prevent moms-to-be from a good night’s sleep.

Not getting enough sleep can have major physical and mental repercussions. Some common side effects are memory loss, a weakened immune system, weight gain, problems concentrating and mood changes. “I don't think people realize what that really does to our brain” says Ebert. “The lack of sleep and how much of an impact it has on our mental health.”

Hormonal changes may play a role
This may be obvious, but pregnancy and childbirth result in major physical changes. Among the notable differences are changing hormones. “The hormones have a huge impact on us,” says Ebert.

During pregnancy, women have significantly higher levels of estrogen and progesterone than nonpregnant women. These hormones help with the development of the fetus and prepares the body for birth and breastfeeding.

Once the baby is born, hormone levels drop drastically. Within two days of giving birth, certain steroid hormones in the mother’s bloodstream decrease by up to 80 percent. Other hormones, such as testosterone and prolactin, also fluctuate in the postpartum period. Some of the hormones associated with pregnancy have been shown to impact mental abilities, although it’s not clear if these hormone shifts are directly related to mom brain. The drops in hormones may influence mood swings or postpartum depression (PPD).

Pregnancy may change your brain
As if sleep and hormone changes weren’t enough for pregnant women or new moms to deal with, pregnancy may actually alter your brain composition. One 2016 study showed that pregnant women experienced a decrease in grey matter in the brain that lasted for at least two years after giving birth.

The study scanned the brains of 25 first-time moms before they conceived and after delivery. For comparison, researchers also scanned the brains of 19 first-time fathers, 17 men without children and 20 women who had never been pregnant. The results showed consistent loss in grey matter for the mothers compared to the other groups.

The affected areas may impact social abilities and processing. Changes in brain composition may help mothers better connect with their children and become aware of their needs. More studies are needed to replicate these findings and research how the changes in grey matter impact cognitive functions.

New mom, new you
Having a child is a lot mentally, physically and emotionally for any mom, so it’s no wonder there may be mental lapses as a result. In addition to everything else new moms deal with, there is a change in self-perception that happens when a woman becomes a mom, which can be overwhelming. As Kimura says, “Just the amounts of changes that happen to you as a person overall, that your identity and who you thought you were suddenly becomes something completely different. Even just trying to rationalize what your new role is, is a challenge for some people.”

Ebert agrees that sleep deprivation, changing hormones and a change in identity can all impact mom brain, but she adds that moms also carry a lot of responsibility. She says that moms end up “holding the ‘mental load,’ which could be everything from her child’s sleep schedule, the complete contents of the diaper bag and the location of each replacement item in the house, a long grocery list, meal ideas for the next several meals including items that might be missing or how to alter it for one family member’s preferences, the time and date of someone’s next doctor/dentist/whatever appointment, how many minutes are left before the dryer is done and when the last time each family member (including the dog) has gone pee.”

New parents should also be aware of the warning signs of PPD and postpartum anxiety. Contact a healthcare provider for any significant changes in mood as this may indicate a more serious condition. For more information about PPD, visit the March of Dimes website. You can also call the Postpartum Support International helpline at (800) 944-4773.

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