Are pregnancy hormones detrimental to cognitive capacities, or do they make the brain resilient to stress and increase memory performance?
The majority of pregnant women complain about memory and concentration problems and a loss of focus. Among the general population these phenomena are referred to as pregnancy dementia or ‘momnesia’. From an evolutionary perspective, pregnancy-related memory impairment may be helpful: women forget about irrelevant stuff and focus on caring for the baby. The question is whether pregnancy hormones raging through the body are harmful to cognitive capacities, or whether they might actually serve some function other than preparing for birth? It appears that the so-called ‘cognitive problems’ related to pregnancy have never been scientifically addressed in humans.
During pregnancy the body starts to dramatically increase the production of the hormones progesterone and estradiol. These two hormones, both involved in preparing the body for birth, are the usual suspects when it comes to ‘momnesia’. Interestingly, it appears that both estradiol and progesterone actually have ‘protective’ effects in the brain. An extensive literature overview by Macbeth and Luine (2010) has demonstrated that pregnancy hormones in animals stimulate the growth and branching of nerve cells and can even generate new nerve cells within the hippocampus, a brain area involved in memory functions. Indeed, in pregnant animals memory performance increases and levels of stress and anxiety decrease.
Studies addressing this issue in humans are rather inconclusive, but they do find some indications that verbal memory is lower during pregnancy. This ‘deficit’ seems to be limited to the third trimester only and disappears again post partum. Interestingly, maternal experience seems to promote cognitive functioning: in mothers, verbal memory, working memory, and attention are better than in females who have never been pregnant before. Moreover, reproductive experience actually provokes a protective mechanism in mothers, which promotes associative learning even long after the offspring have left their care.
I suppose we can conclude that although pregnant women complain about memory loss, this subjective form of momnesia is only partly supported by scientific evidence. At least in animals pregnancy hormones seem to stimulate brain growth and tend to (indirectly) increase cognitive capacities. It appears that it is not just the period of pregnancy that is important, but that maternal experience also contributes to these processes. This, however, does not need to have hormonal origins per se, but can also depend on increased demands of the family environment requiring more ‘efficient’ thinking. So would one expect the same phenomenon to occur in fathers?