Is ‘momnesia’ a real condition or an urban myth?

Vancouver-based researchers investigate the impact of pregnancy, including the child’s sex, on memory and cognition

By Chad Skelton, Vancouver Sun – May 8, 2010, p. A23

Liisa Galea is an award-winning researcher at the University of B.C. with a PhD in neuroscience.

So it was more than a little embarrassing for her when, pregnant with her second child, she couldn’t remember where her car was parked.

She knew she’d left it in the parkade across the street from her UBC office. But, for the life of her, she couldn’t recall what level she was on.

Even worse, this didn’t happen to her just once or twice—but nearly a dozen times throughout her third trimester.

Galea is far from the first woman to forget things during pregnancy, a phenomenon so common it goes by many names: “momnesia,” “baby brain” and “dumb Mom syndrome.”

But as an expert in the field of neuroendocrinology—the link between hormones and the brain—Galea was in a unique position to figure out what was going on.

In the decade since her parking problems, Galea has undertaken a number of studies on the impact of pregnancy on the brain, mainly on rats.

She’s found that pregnant rats are worse at making their way through mazes than non-pregnant rats and that their hippocampus (an area of the brain key to memory) is smaller.

And Galea’s just one of several Vancouver-based researchers trying to figure out whether “baby brain” is a real condition or just an urban legend.

Forgetful or just distracted?

On the face of it, the notion that having a child might impact a woman’s brain function is not that surprising. There’s plenty of evidence that hormones can affect thinking. And pregnancy has a uniquely dramatic effect on hormone levels—estrogen, for example, can reach concentrations 1,000 times normal.

When surveyed by researchers, almost all pregnant women say they suffer at least some memory problems and difficulty focusing.

But studies that try to test pregnant women’s memory in the lab have been decidedly mixed: some studies find they perform worse than non-pregnant women while others have not. Carrie Cuttler, a post-doctoral fellow at UBC and a colleague of Galea’s, began to wonder whether the lab itself might be the problem.

In a not-yet-published study, Cuttler and her colleagues asked 60 pregnant women and 24 non-pregnant women to perform a series of memory tests in their lab, such as repeating back a list of words.

As expected, the pregnant women did as well as the nonpregnant women on almost all the tests.

But that wasn’t the end of the study. As the women were leaving, Cuttler gave them a short, one-page questionnaire and asked them to mail it back to her the next day.

“It was stamped, it was addressed, it was ready to go,” said Cuttler. “All they had to do was pop it in the mailbox.”

Which is exactly what 70 per cent of the non-pregnant women did.

And the pregnant women? Just over half of those in their second and third trimester remembered to mail the letter.

And only one in four of those in the first trimester mailed it back.

Cuttler says the fact so many “baby brain” studies are conducted in the lab may be masking the extent of the problem—because for a harried, pregnant woman, a lab may be the first moment’s peace they’ve had all week.

“Pregnant women can perform on these cognitive tasks with little difficulty when they’re in a sterile, distraction-free environment, where they can focus on the task at hand,” she said. “But if you put them in the real world where they’ve got … family issues [and] work issues, their attention is much more divided. They have a lot more going on. That’s when you see the deficit.”

Cuttler said her study also suggests that “baby brain” may have less to do with brain chemistry and more to do with the sheer number of things a pregnant woman has to think about, from prenatal vitamins to doctor’s appointments.

That may explain why women in the first trimester—who’ve had the least amount of time to get used to being pregnant—fared the worst in Cuttler’s study.

A nice thing about her study, said Cuttler, is that it suggests pregnant women’s mental performance in the workplace need not suffer.

“If you put a pregnant woman in a quiet, distraction-free environment she can perform as well as a non-pregnant woman,” said Cuttler. “Maybe just don’t ask her to do a hundred things at once.”

Baby’s sex a factor

How many distractions a pregnant woman has in her life may not be the only thing affecting her brain.

Whether she’s carrying a boy or a girl also seems to make a big difference.

A few years ago, Neil Watson, a psychology professor at Simon Fraser University, conducted a study that looked at how 39 pregnant women—26 carrying boys, 13 carrying girls—performed on tests of their memory from early pregnancy to several months after delivery.

The study found a surprisingly significant gap in memory performance based on the sex of the mother’s fetus: those carrying boys scored about 25 per cent better on memory tests than those carrying girls.

Watson said he’s curious what’s behind the gender gap and is conducting followup research to try to figure out what’s going on.

One of the most puzzling aspects of the original study, he said, is how persistent the gender gap was.

Boys release different hormones into their mother’s system than girls. If that’s the cause of the memory gap, said Watson, you’d expect the gap to be much wider at some stages of pregnancy than others.

Instead, his study found the gap between “boy moms” and “girl moms” persisted from the first test, at eight weeks gestation, until months after delivery.

Which raises another, far more controversial possibility, said Watson: That carrying boys doesn’t necessarily make women smarter. Rather, smart women may be more likely to have boys.

Watson stresses he has no evidence yet to support this hypothesis—and said that, as a father of three daughters, he’s not personally advocating it.

But he notes that, in other species, it’s been shown that females can sometimes bias the sex of their children when having one gender or the other is an evolutionary advantage.

Whether humans might do the same, he said, is a “fascinating possibility.”

The possible reverse effect of motherhood

Having experienced baby brain firsthand, Galea sympathizes with women who worry being pregnant is making them dumber.

And she notes the research on the topic isn’t all discouraging.

For example, take those rats who fumbled their way around Galea’s mazes during pregnancy.

When Galea tests rats later in life, after their children have left the nest, they perform better than rats who’ve never had kids.

And other studies have suggested mother rats are less susceptible to degenerative brain illnesses like Alzheimer’s than non-mother rats.

No study has yet been done looking at the long-term effects of motherhood on the human brain.

But Galea can’t help but think that, if pregnancy impairs memory and cognition, the long-term mental effort involved in being a mother might actually do the opposite.

“When you’re a mom you’ve got to remember your kids’ doctor’s appointments, their dentist’s appointment, their shots,” she said.

“Before you were just taking care of yourself. Now you’re taking care of another human being.”