Alzheimer’s disease researcher J. Galen Buckwalter was investigating the effect of hormones on brain function when he and collaborator T. Murphy Goodwin came upon a pattern of impairment in certain brain functions in women in late pregnancy.

Photo by Irene Fertik

Women have long talked about “pregnancy brain,” a sense of not feeling in top intellectual form in the month or two before giving birth. Obstetric nurses have even coined the expression “pregnancy-induced slowness” to describe the difficulty some pre-delivery patients have in recalling instructions.

Now a new study by neural science researchers at USC offers concrete evidence that intellectual functioning is, in fact, depressed in women in the time immediately before childbirth.

The deficit in certain cognitive areas – notably in the ability to remember new information – is striking. Women performed 15 percent to 20 percent worse when pregnant than after delivery in tests recently conducted by J. Galen Buckwalter and collaborators at the Andrus Gerontology Center.

The results were made public Wednesday, Feb. 5, in a presentation at the International Neuropsychological Society annual meeting in Orlando, Fla.

Buckwalter and his group tested a sample of 19 women in the month before they gave birth and again two to five weeks after the arrival of their babies. The tests included a battery of standard tests of intellectual functioning, along with tests of mood and affect designed to make sure that any cognitive changes found were not attributable to anxiety, high excitement or another emotional state.

On the California Verbal Learning Test scores, Buckwalter observed marked declines in the women’s ability to recall lists of words and objects, compared with the same women’s abilities after their babies were born.

“The decline was often quite dramatic,” Buckwalter said. “More than 70 percent of the women tested had difficulty in learning new information. They tended to be easily distracted and to have notable difficulty in tracking more than one piece of information at a time. Their performance was far below what would be expected of nonpregnant women of the same age and education levels.”

Buckwalter, a research assistant professor of gerontology at the Andrus Gerontology Center, is a specialist in Alzheimer’s disease and the influence of hormones on neurological functioning.

Statistically, the test results were highly significant: Score changes were so drastic that chance alone could account for them only twice in 1,000 trials, Buckwalter said.

Anecdotal correlation of the effect was noted by study collaborator T. Murphy Goodwin, associate professor of obstetrics and gynecology at the School of Medicine and a practicing obstetrician at Good Samaritan Hospital in Los Angeles.

“I find that many patients have trouble recollecting things, or difficulty keeping track of things, toward the end of their pregnancy,” Goodwin said. “In many cases, they wind up making notes to themselves to remem- ber things. Nurses sometimes joke about what they call PIS – ‘Pregnancy-Induced Slowness.’

“Most clinicians don’t focus on the phenomenon, particularly since most patients devise effective methods of coping with it,” he said. “Still, I think most of us are aware, on some level, that we have to repeat instructions more frequently to late-pregnancy patients.”

Buckwalter and his group are trying to find an explanation for the phenomenon, which is the reverse of what they had expected to find.

“The hormone estrogen generally improves brain functioning, and estrogen levels increase drastically during pregnancy,” he said. “Numerous other hormones, such as progesterone, dehydroepiandrosterone (DHEA) and cortisol, also change dramatically during pregnancy. If we can determine what hormone is causing these effects, we will have a new lead on how hormones affect the brain.”

Recently reported research from England may offer another clue: Imaging studies performed at the Royal Postgraduate Medical School in London found that women’s brains actually undergo shrinkage – short term and reversible, but significant – during pregnancy.

“We plan more studies to try to understand the phenomenon better,” Buckwalter said, “but it does appear to be real. If nothing else, recognition of the phenomenon’s reality should give late-term pregnant women, and the people who deal with them, more patience and understanding.”

Other members of the research team include Carol A. McLeary of the medical school’s department of neurology, and Fuller Theological Seminary graduate students Kate R. Leung, Brendon W. Bluestein and Deborah K. Payne, who administered the tests. The research was supported by National Institutes of Health grant AG05142.