Question
Does a woman's brain shrink during pregnancy?
Answer
Mostly yes.
Explanation
A 2002 study measured the brain and ventricular size before and after pregnancy of 14 women. Results showed a gradual decrease in brain size (and increase of the lateral ventricles) during pregnancy, and a return to the original sizes in up to 6 months after pregnancy.
Studies on the cognitive changes related to pregnancy are mixed, with most studies finding some level of cognitive impairment during pregnancy which is relieved after delivery. However, it has not been shown that the temporary brain size reduction during pregnancy is the cause of any cognitive impairment.
Sources
Buckwalter, J.G., F.Z. Stanczyk, et al., Pregnancy, the postpartum, and steroid hormones: effects on cognition and mood (Psychoneuroendocrinology, July 1999)
Logan, D.M. K.R. Hill, et al., How do memory and attention change with pregnancy and childbirth? A controlled longitudinal examination of neuropsychological functioning in pregnant and postpartum women (Journal of Clinical and Experimental Neuropsychology, 2014)
Oatridge, A., A. Holdcroft, et al., Change in Brain Size during and after Pregnancy: Study in Healthy Women and Women with Preeclampsia (American Journal of Neuroradiology, January 2002)
Parsons, T.D., E. Thompson, et al., Pregnancy history and cognition during and after pregnancy (International Journal of Neuroscience, 2004)