“Most pregnant women will admit to bouts of “pregnancy brain” or “mommy brain” — whether it’s forgetting doctor’s appointments or forgetting their own phone number. This pregnancy-induced mental fog is part of the neurological changes at the start of pregnancy that continue throughout postpartum. ”
I am not at all sure that this phenomenon really exists, but scientists at Barcelona University recently published results from their study of 25 first-time pregnant women, the 25 fathers responsible for the pregnancies, and 20 non-pregnant childless women. By comparing “before conception” and “postpartum” MRIs in the pregnant women the researchers documented a definite reduction in the pregnant women’s gray matter. The volume loss of gray matter occurred in three specific areas of the brain associated with social cognition and emotional feelings. The differences of volume in the pregnant women was so apparent that the researchers could accurately pick which women were pregnant just by looking at the MRIs. Similar MRI imaging of the fathers and non-pregnant women showed no reduction of gray matter.
Gray matter is the part of the brain cortex that is mostly neuronal cells. White matter consists mostly of connections between the neuronal cells, axons (“wires”) coated with white myelin. The reduction of gray matter in the pregnant women was in brain areas associated with “being able to think about how other people feel and perceive things.” and persisted for 2 years after delivery.
Using fMRI (functional MRI – measures brain activity not just structure) these reduced gray matter areas would “light up”, show higher metabolic activity, when the mother gazed upon a picture of her own baby rather than a picture of someone else’s baby. The researchers speculated that this was a measure of quality “mother-infant attachment”.
The implication of this gray matter reduction is not clear. Many past studies in all kinds of people suggest strongly that people with larger volume of gray matter have better memory and are happier.
A study of ultra-marathoners (ran 2,788 miles in 64 days without a rest day) showed a reduction of gray matter of 6%, but it was reversed in 6 months and was not associated with any brain lesions. In comparison to the less than 0.2% per year gray matter reduction in the elderly this 6% is H-Y-U-G-E. Pre- and post-run Cognitive tests would have been help in this study of ultra-marathoners, but I am not sure you could detect any increase in stupidity in them. Presumably the reversible reduction in brain volume was due to dehydration.
Studies of chronic marijuana users show reduction in gray matter, but increased “connections”, and no loss of cognitive skills (if not high at the time of testing). This and similar findings in adolescent brains have been explained as either a bad thing about marijuana use or as a “maturation” of the brain as it gets “better organized” for specialized tasks. A similar explanation of an “organizing process”, “a pruning toward a more efficient brain” is offered by the researchers of these pregnant women.
So where does this leave us regarding permanent gray matter reduction in pregnant women? We, of course, don’t really know at this point. fMRI studies are still in their infancy, and there is some controversy about what they really mean. But, cognitive tests of both these pregnant and non-pregnant women showed no difference, and no change in cognitive functions after delivery, so we can confidently say that pregnancy does NOT make you “stupid”… or even “stupider”.