I used to have a good memory. I could remember friends’ birthdays, anniversaries and phone numbers. I never lost track of project timelines or due dates. I knew where everything was (mostly) and could find it when I needed it.
That was before I experienced two extreme endocrine events — that was before I had children.
If you have children, or know someone who has children, you might guess what happened next. My amazing memory for details big and small disappeared, seemingly overnight. By the time my second child was crawling, I had begun to think I needed a list of those things I shouldn’t forget tattooed on the back of my hand. Unfortunately my hand is really not that big.
So what causes this phenomenon, affectionately termed “Momnesia” or “Mommy Brain”? I wish I could tell you that I knew or that scientists know. Unfortunately, research in this area is still very much in its infancy, but there are scientists studying these things, and I thought I share what I have learned from this paper (1).
First, it is not just me. Up to 80% of women report impaired cognitive function during pregnancy, and this is supported by empirical data from investigations of memory function during pregnancy. Deficits in two areas of memory, recall and the executive component of working memory, persist into the postpartum period. If you are one of the roughly 20% who don’t report experiencing this phenomenon, count yourself lucky! For the rest of us, here is some of what science has learned.
First, there is a connection between the hormones that flood a woman’s body during pregnancy and memory dificulties. In 2010, Glynn identified an association between the hormones estradiol and cortisol and both prenatal and postpartum memory impairment (2).
In a woman’s life span there is no naturally occurring event that results in the endocrine system producing more extreme hormone levels than those produced during pregnancy. While scientists do not know a lot about how these hormone exposures affect the brain, they do know quite a bit about how two less extreme endocrine events (puberty and menopause) influence changes in both brain structure and function. Finally animal studies have shown that reproduction produces changes in animal brains that are life-long and not limited to areas directly involved with maternal behavior.
What we do know about humans suggests that, as in animals, hormone exposures experienced during pregnancy help prepare the human brain for the challenges of motherhood. Prenatal estrogen, cortisol and oxytocin levels seem to influence early postpartum care by mothers. A relatively new study found that the gray matter volumes in areas of the brain associated with maternal motivation and behavior increase during the early postpartum period (3). Mothers who had the most positive feelings toward their baby showed the greatest increase in gray matter.
Are you ready for the final blow? Animal studies also suggest that the effects of pregnancy on cognition and other areas are additive, meaning they are amplified with each pregnancy.
I want to emphasize that almost none of this has been studied in humans, instead this information is largely extrapolated from animal models and studies. However, what we do know about humans correlates well enough to the animal data to make these predictions reasonable.
Well there you have it. I hope you have enjoyed my brief explanation of a possible cause of Mommy Brain. And I hope I remember to post this on Wednesday.
- Glynn, L. and Sandman, C. (2012) Prenatal origins of neurological development: A critical period for fetus and mother. Curr. Dir. Psychol. Sci. 20, 384–9.
- Glynn, L. (2010) Giving birth to a new brain: Hormone exposures of pregnancy influence human memory. Psychoneuroendrocrinology 35, 1148–55.
- Kim, P. et al. (2010) The plasticity of human maternal brain: Longitudinal changes in brain anatomy during early postpartum period. Behavioral Neuroscience 124, 695–700.