No Evidence of Cognitive Decline in Pregnant Women, New Mothers

Pauline Anderson

February 11, 2010

February 11, 2010 — It appears that the image of the dotty pregnant woman or the scatterbrained new mom is just an urban myth. New research shows that there is no evidence of cognitive decline during pregnancy or after giving birth.

"Pregnant women and new mothers might be distractible, but when the power of their intelligence is turned to a task, there’s absolutely no evidence that they’re impaired relative to nonpregnant women," lead Helen Christensen, PhD, Australian National University, Canberra, told Medscape Psychiatry.

Obstetricians, family doctors, and midwives may want to take note of these findings that suggest that "placenta brain" is not inevitable, she said.

The study is published in the February issue of the British Journal of Psychiatry.

For the study, researchers measured baseline cognitive performance of 1241 women aged 20 to 24 years who had been randomly selected from the electoral role. These women had not been pregnant or given birth when the study began in 1999. Researchers tested the following 4 areas of cognition:

  • Cognitive speed;

  • Working memory;

  • Immediate recall; and

  • Delayed recall.

Historical Data

"We have the historical data on these women, so we know what they were performing like beforehand," said Dr. Christensen. "Most of the research has recruited women when they’re already pregnant, so you get a potential for bias in selecting women who might be concerned about their memories during pregnancy."

Women in the study did not know that the researchers were conducting cognitive testing as it relates to pregnancy, said Dr. Christensen.

Of the initial sample, 1126 and 1058 participants completed follow-up tests in 2003 and 2007, respectively. During the 3 study waves, 73 of the women became pregnant and 188 became first-time mothers. The researchers assessed women who became pregnant or gave birth between 1999 and 2003 separately from those who became pregnant or new mothers between 2003 and 2007.

The researchers found no significant differences in cognitive change from waves 1 to 2 between those who were pregnant and those who were not on tests of cognitive speed and immediate and delayed memory recall.

However, women who were pregnant at wave 3 remembered approximately 1 fewer backward digit (Digit Backwards subtest) than women who remained nonpregnant.

Isolated Finding

However, this was an isolated finding that did not remain significant after adjusting for multiple testing and after both waves were combined, said Dr. Christensen.

"The women slowed down somewhat, and it looked like there might have been a short-term effect, but when we combined the samples and looked at the next cohort, it wasn’t reliable. I think it was a by-chance finding."

The researchers also found no significant differences between those women who had become mothers and those who had not. They also compared mothers who had older and younger infants and found no cognitive difference between women with infants younger than 12 months and those with infants older than 12 months.

The researchers took into consideration various potential confounders. "We controlled for sleep and for levels of depression, education, and other variables that might interact, but we didn’t find any effects of those overall," said Dr. Christensen

"That doesn’t mean that women aren’t chronically tired and fatigued when they’re having a new baby. I guess the results may be even stronger because they may have been at a disadvantage," she added.

Pregnancy Manuals

According to Dr. Christensen, pregnancy manuals often tell women they are likely to experience memory and concentration problems, so women and their partners might more readily attribute a memory lapse to the pregnancy.

Earlier research that showed a connection between pregnancy and decreased cognition helped perpetrate the myth. But these studies may have included women who were more concerned about the effect of pregnancy on their cognitive status or been more depressed or sleep deprived.

As well, said Dr. Christensen, this earlier research was based on recruiting women at the time they are pregnant and comparing them with controls, rather than following up women as they become pregnant and new mothers.

The research is important because it dispels the stereotype of pregnant women or new mothers as performing suboptimally.

In terms of employment and putting women on important tasks, there may be a tendency to think "Oh well, she’s pregnant, so maybe she won’t be fully on the ball," said Dr. Christensen. "That attitude still exists. I think our study challenges that idea and shows that women have exactly the same level of functioning."

Dr. Christensen and her colleagues plan to continue to follow up the cohort. To date, 542 of the participants — just fewer than 50% — have not yet become pregnant or new mothers, so there will likely be a larger study base in the future. "It will be interesting to see if older mothers are more prone to losing cognition," said Dr. Christensen.

Challenge to Old Myths

Commenting on the findings, Kenneth Heilman, MD, codirector, University of Florida Cognitive and Memory Disorder Clinic, Gainesville, said the study was "beautifully done" and included "excellent tests of working memory and verbal memory." He said there is no question that these results will challenge old myths about memory during pregnancy.

However, Dr. Heilman would like to have seen what he called "state-dependent" memory included in the study. Pregnant women may not so much experience loss of memory but a "change of state" due to altered hormones, he said. "There are certain memories that you recall because your brain is in a certain state, and the states can be medications you take, or alcohol, and a zillion other things."

For this, researchers would have had to ask the women to remember something before they became pregnant and to recall it after they got pregnant and vice versa — have them remember something while pregnant and recall it after giving birth.

Dr. Heilman also would like to have seen a spatial memory test included in the study to determine whether a change in hormones alters spatial skills during pregnancy.

The study authors have disclosed no financial relationships.

Br J Psychiatry. 2010;196:126-132.

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