In graduate school I studied this issue and completed several studies on pregnancy and postpartum mood and memory changes. In one such study, I ran a full battery neuropsychological tests on a group (n = 28) of highly educated, healthy, medication free, first-time moms. We tested in late pregnancy and within 10 days following the delivery of the child. We also measured a range of hormones (progesterone, DHEAS, testosterone, estrone, estradiol and estriol) to determine what relationship the radical hormone changes of pregnancy and childbirth had on a woman’s cognitive ability. We knew from animal research that steroid hormones could affect learning in very significant ways. It wasn’t that difficult to suspect the same would be true of human women.
The study was never published, rejected from at least three, maybe four journals and has been sitting in a file ever since (along with a number of other studies). With the open access and open science movements growing, I decided it was time for this research to see the light of day. I will be self-publishing much of my research over the coming weeks and months. Here is the first study. Understanding Maternal Cognitive Changes: Associations between Hormones and Memory.
Is the Mommy Brain Real?
More importantly, are hormones to blame? The answer is yes on both counts. We found that pregnant and postpartum women exhibited detectable cognitive deficits across multiple domains. The deficits were worse in late pregnancy and mostly improved postpartum. These memory problems were linked to both the excessively high hormones of late pregnancy, the low hormones following delivery and the large changes in hormone concentration from pregnancy to postpartum.
What Types of Cognitive Deficits?
Pregnant and to a lesser degree, postpartum women had difficulty sustaining focus – this may be the mommy brain fog that many women complain of. We also found that during pregnancy especially, women were unable to manipulate and organize incoming information effectively. This presented as poor performance across a number of tests that assessed both short and long term memory.
In the case of verbal memory, these highly intelligent (estimated average IQ was 114 – 119) and educated (average years of education was 16 years) women tested in the low single digit to the 20th percentiles across multiple IQ-adjusted verbal recall measures. Even when estimates of IQ were not used to adjust scores, the participants performed poorly compared to normative standards. This was surprising given that many of these women had advanced degrees and were working in professional capacities.
The verbal tests involved remembering lists of words; words that could be grouped into meaningful categories that would improve memory significantly. Most of the study participants had difficulty grouping the words into categories. Instead, they would attempt to remember by rote sequence, which is always much more difficult. They also exhibited high numbers of intrusions – recalling words that were not in the original lists and repetitions – repeating words.
Similarly, and more strikingly visible, visual- spatial memory was marred by the inability to group bits of information and perhaps even to see the groupings in the first place. In this test, the study participants were given a complex figure to copy (shown below). They were not told that they would be asked to recall and redraw the picture later. When asked to redraw the figure, the inability to see the totality of the picture, to group bits of information was apparent.
Does Memory Improve Postpartum?
Interestingly, while spatial memory improved significantly from pregnancy to postpartum, verbal memory did not. And this is probably what troubles women the most, the perceived deficits in verbal memory. Most of us think in words, when our ability to find words, retain words, organize information effectively is compromised, we notice.
Hormones and Memory
Both high levels of late pregnancy estrogens, (estrone, estradiol and estriol – we measured all three) and the low levels these estrogens postpartum were correlated with multiple measures of diminished memory, attention and processing. Additionally, the larger the change in the circulating levels of estrogens from late pregnancy to early postpartum was associated with poor memory postpartum. Indeed, women who had higher postpartum estradiol and estriol specifically, performed better on measures of verbal memory than those who did not.
Progesterone, long thought to be associated with cognitive function, primarily because of its sedative properties, was not associated with any measure of cognitive function at either test time, although large changes in progesterone were associated with some performance measures. DHEAS and testosterone, not often measured in pregnancy, postpartum or even in women’s health in general, were also associated with a few measures of cognitive functioning.
What This Means
Ladies, you are not imagining the pregnancy memory problems. They exist and they are related to the hormones. Most women knew this already, but it took a while for science to catch up. Not to worry though, the memory problems do resolve as the hormones stabilize (my next study to be self-published – a long term follow-up). Read the full study for all the details: Understanding Maternal Cognitive Changes: Associations between Hormones and Memory.
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This article was originally published on Hormones Matter on March 26, 2013.