PREGNANT WOMEN’S BRAINS SHRANK, THEN REBOUNDED BY 6 MONTHS
A small 2002 MRI study found brain size during pregnancy shrank, then bounced back within about six months of delivery.
The research, published in the January 2002 issue of the AJNR American Journal of Neuroradiology, tracked nine healthy pregnant women. It also followed five age-matched women with preeclampsia, one mild case and four severe.
“The changes follow a consistent time course in each woman,” the study authors wrote in the abstract.
The paper noted that the pituitary gland was already known to grow during pregnancy. What pregnancy did to the brain as a whole was not known when the study began.
What the scans showed
Researchers took 3D MRI brain-volume images and used image registration and semiautomated software to calculate brain and ventricular volumes.
Only a handful of the healthy women were scanned during pregnancy itself. In those women, brain volume fell and ventricular volume rose, with the biggest changes measured at term.
Two healthy participants had been scanned before they conceived. At term, their brain volumes were down 4.1% and 6.6% compared with those earlier scans.
After delivery, the pattern flipped. Brain volume rose significantly and ventricular volume dropped in the healthy group.
By about six months postpartum, measurements in the women scanned before conception showed little evidence of difference from their preconception numbers.
The preeclampsia group
The five women with preeclampsia were scanned shortly before delivery and again afterward. All five showed the same overall pattern: brain volume going up and ventricular volume going down after birth.
Their measured brain volumes were significantly smaller than the healthy group’s before delivery and at several points afterward. The study found no difference by the final comparison.
It found no significant difference in ventricular size between the two groups at the time points compared.
What the study did not say
The paper measured changes in volume. It did not establish that brain tissue was lost and then regenerated, and it did not link the shifts to pregnancy-related memory or attention problems.
The authors were blunt about the limits. “The mechanism and physiologic importance of these findings are speculative at the present time,” they wrote in the conclusion.
What happened next
A separate study took a much closer look at one woman.
That study, published in Nature Neuroscience on September 16, 2024, followed a single participant with MRI scans from before conception through two years after she gave birth, the National Institutes of Health reported.
Total gray-matter volume and cortical thickness decreased during pregnancy, then partially rebounded after birth. Lateral-ventricle volume increased in the second and third trimesters and dropped sharply after delivery.
The researchers reported that the changes were associated with shifts in steroid-hormone levels.
The authors of the 2024 study said few brain regions were “untouched by the transition to motherhood,” BrainFacts reported.
