Wellness·4 min read

What Actually Causes Pregnancy Brain? A Gynecologist Explains

A woman sitting on the couch holding her pregnant belly with her forehead resting on her other hand
Design: theSkimm | Photo: iStock
December 14, 2022

There are a lot of symptoms you might expect from pregnancy — craving certain foods or being exhausted all the time, for example. Pregnancy brain might not have made the list, but forgetfulness and brain fog is something a lot of pregnant women experience. Let's face it, it's not a fun side effect.

What’s also not fun: Experts still can't pinpoint what causes pregnancy brain. To get to the bottom of what we do know, we called up gynecologist Dr. Alyssa Dweck.

What is pregnancy brain? 

The forgetfulness, brain fog, and inattention that many people experience during pregnancy and in early motherhood. You may know it as “mommy brain” or “baby brain.” It’s that feeling when you can’t remember names of common items, when you forget what you’re saying mid-sentence, or try to start the car with your phone charger instead of your keys. IYKYK. 

Is pregnancy brain real?

If you’re pregnant or a new mom, and you just tried to wash your clothes in the dishwasher, first, no judgment. Second, you know that pregnancy brain is more than real. Anecdotal evidence shows that you’re definitely not alone: Up to 80% of new moms say they’ve felt it. That said, pregnancy brain isn’t an official medical term or clinical diagnosis. That’s because experts are still trying to understand what’s exactly happening physiologically.

So, what causes pregnancy brain fog?

Experts can't agree on a specific reason for why pregnancy brain happens, or if it's even real at all. Some research suggests pregnancy causes changes in the brain, but so far it’s been inconclusive. Some experts believe there may be other potential causes, like…

  • Hormones. “Any major hormonal disruption in the system can cause this type of thing,” says Dr. Dweck. The hormones in question: Progesterone and estrogen, which increase in the second and third trimester. 

  • Sleep deprivation. You don’t need anyone to tell you that restful sleep is hard to come by during and after pregnancy. “Whether it's having to get up to urinate a thousand times, having some anxiousness about what's to come, or having other kids to take care of,” you’re dealing with a lot, says Dr. Dweck. It’s no coincidence that sleep helps consolidate and reinforce memories. Without it, your brain might not be operating at 100%.

  • Stress and anxiety levels. Both can sometimes cause brain fog. 

It’s not all bad news: Pregnancy brain may be a kind of “mom superpower” that prepares moms to better understand their baby’s needs and handle stress

When does pregnancy brain start, and how long does it last? 

It may start as early as the first trimester. (As if morning sickness and heartburn aren't enough.) Though some studies suggested it could start later. There’s no concrete end date. But one 2016 study found the effects of pregnancy brain lasting for two years after giving birth. Ah, the joys of motherhood.

What are tips to cope with pregnancy brain fog?

Start by having compassion for yourself. Recognize that your body is going through a lot — and that you might not be at 100% all the time. There are a few other things you can do to support yourself: 

  • Try eating food that supports brain function. Go ahead and add blueberries, eggs, and spinach to your grocery list

  • Stay hydrated. Dehydration may worsen your memory and attentiveness. Pro tip: Get yourself a cute water bottle to encourage yourself to drink more H2O. 

  • Try puzzles or brain games. Think of them like workouts for your brain. 

  • Make lists or set reminders on your phone. Even for things like brushing your teeth, making appointments, and locking doors. No reminder is too small. 

  • Take a nap. Try to do it early in the day to try and catch up on sleep, says Dr. Dweck. Easier said than done, but it may help you feel more clear-headed.

  • Communicate to your partner. Let them know what’s going on so they can support you. Especially if they haven’t “physically experienced this type of thing themselves,” says Dr. Dweck. 


There’s still a lot left to learn about what happens to the brain during and after pregnancy. But what you’re experiencing is very real. So be kind to yourself and do what you can to get through it. One thing you don’t want to forget: That your brain might be changing in order to prepare you to be a great mom. 

Updated on June 29 to reflect new information.

This content is for informational and educational purposes only. It does not constitute a medical opinion, medical advice, or diagnosis or treatment of any particular condition. 

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