Pregnancy is a time of dramatic change for all expectant mothers.

Hormones are surging, bellies are growing, ankles are swelling.

The biggest changes, many of which can be seen with the naked eye, are quite predictable.

And now the changes that can’t be seen might become a little clearer now, thanks to new research.

A study published this month in Nature Neurosciencesheds light on the substantial changes that occur in a woman’s brain during pregnancy.

Namely, the brain gets smaller and it also makes itself more efficient.

These changes, according to the study, prepare an expectant mother for the important work of parenthood.

Researchers at universities in Spain and the Netherlands are the first to use computer imaging (specifically MRI) to measure how the brain’s structure changes because of pregnancy.

While scientists have known for some time how pregnancy affects the brains in rodent mothers, they’ve never had a clear understanding of what happens in humans.

This study reveals some key ways pregnancy impacts a woman’s brain.

Read more: Men and women’s brains are wired differently »

Changes in the brain

The study showed a reduction in the gray matter of the brain.

Think of gray matter as the part of the brain that performs tasks.

The biggest loss of gray matter was in the front and temporal lobe regions.

These areas of the brain are responsible for a variety of tasks, including social cognition. That’s the ability to interact with others.

Gray matter loss occurs in specific areas of a new mother’s brain.

These areas are the ones that help to understand other people’s feelings, beliefs, and nonverbal signals. These areas also help form attachments to people.

Losing gray matter in these areas may sound worrisome, but there’s good news.

The researchers found that women who experienced greater gray matter loss in those areas also had greater feelings of attachment to their infants.

Additionally, these women also felt fewer negative emotions toward their babies.

So while areas of the brain “shrink,” they became more powerful.

For new moms, this means their brains could be preparing to better interpret newborns’ body language, including various cries and coos.

These changes can also help new moms detect threats so they can protect themselves and their babies more quickly.

Lastly, these changes open mothers up to deeper, stronger bonds with other people, specifically a new bundle of joy.

Read more: Women’s brains affected more by drug abuse »

Dads aren’t affected

This study looked at the brains of 25 women before they were pregnant and again three weeks to two months after their first babies were born.

The researchers also studied the brains of 19 first-time fathers.

They concluded the changes to the brain’s structure only occurred in mothers, not fathers.

To understand the impact of pregnancy and parenthood on the brain, the researchers also studied 20 women who had never been pregnant and 17 men who didn’t have children.

The study found nearly identical changes in the brains of women who conceived naturally and those who used in vitro fertilization.

Read more: How men and women process emotions differently »

Your memory isn’t missing

New moms often report experiencing frequent forgetfulness or lack of recall before and after giving birth.

This pregnancy-induced memory loss or “baby brain,” as many moms call it, wasn’t reflected in the researchers’ findings.

In fact, the study found there was no change in a mom’s cognitive ability after pregnancy compared with her ability before she became pregnant.

Read more: Why male and female brains react differently to stress »

Changes have staying power

The investigators were curious how long this reshaped brain might last, so they asked the mothers to return for final scans two years after their babies were born.

Of the original 25 mothers, 11 women had not given birth to a second child or were not pregnant again during this time.

These scans found that the changes detected in the new mothers right after a baby’s birth remained.

Read more: What happens during the trimesters of pregnancy »

The brain-baby connection

If the thought of a shrinking brain is alarming it shouldn’t be, says Robert Froemke, PhD, neuroscientist at New York University’s Langone Medical Center.

Instead, think of it as the brain is making itself smarter and more efficient.

“There’s a difference between ‘an apparent reduction in gray matter’ and ‘the brain shrinking,’” he told Healthline. “The brain itself doesn’t shrink. It’s not at all clear what actually goes on when gray matter is reduced.”

Froemke offers an easier way to understand this change.

“Think about this as a form of ‘spring cleaning.’ It’s making things more organized, streamlined, coherent to prepare mothers for the complexity and urgency of childcare,” he said. “If neurons are closer together, or neural connections reorganized to disregard irrelevant synapses and preserve important synapses, or otherwise able to more effectively, reliably, and rapidly process critical information, it’s easier to imagine why this might make sense, and help the maternal brain respond to the needs of her baby.”

Thanks to the study, it’s now known the brain maintains this new architecture for at least two years after delivery.

This reorganized hierarchy may mean expectant mothers may feel like their brains aren’t functioning the way they were pre-baby. Now, we know that’s the truth.

That doesn’t mean, however, there will be memory loss. “Baby brain,” as this study pointed out, isn’t detectable.

“The study reports no change in memory — at least in the kinds of things tested by the authors. They probably can’t test everything, especially complex real-world things like buying milk and diapers,” Froemke said.

Now, other things have taken priority in the brain. Forgetting to buy milk or accidentally not recording that new show on cable?

That’s frustrating, but now remembering a 3 p.m. feeding and managing to mentally note every wet or dirty diaper for the past 48 hours is possible.

For a new parent, that is what’s important.

Forgetting diapers or accidentally driving past the dry cleaners’ may not be caused by the brain changes. Instead, they may be the result of stress-induced changes all new parents experience. In other words, that’s normal.

After all, the new mother is focusing on the new baby. They’re solving different problems and thinking about things in their environment and life differently. There are new priorities and tasks.

That doesn’t mean losing memory or mental capabilities. Life is, well, different now.

“Parenting — particularly motherhood — is among the most complex and stressful set of events and behaviors we experience in our lives. Thus it’s no surprise that a number of changes occur in our brains when we become parents. Taking care of another person, especially a helpless infant, is a lot of work and can demand much or all of our attention,” Froemke said. “Of course, it’s wonderful and rewarding, but that doesn’t make it any less difficult.