Pregnancy is a time filled with many emotional and physical changes: the sense of smell increases, the whole body grows to accommodate the growing bundle of joy, mood swings may be in full effect, and many women have “pregnancy Brain” – the frustrating moments of forgetfulness that seem to happen more and more often. But what if I told you that your brain actually changes shape during pregnancy, too? Many women say they feel their body is never the same afterward; now we know neither is their brain.
A recent study published in the journal Nature looked at before and after brain scans of first-time mothers (primiparous) and their counterparts who had not yet had children (nulliparous) and found there is a significant change in the gray matter volume and morphology in the areas associated with social interactions. These regions are associated with the ‘theory-of-mind’ network, the ability to assign and perceive beliefs, emotions, and desires of oneself and of others — a very important skill set for a new mother who must now interpret the wants and needs of a speechless baby.
What drives this change? The amplification of hormones circulating through the body, of course! Sex hormones regulate the number and shape of your neurons, so it stands to reason the upsurge of estrodiol/progesterone would have profound effects on your neural network. Progesterone is increased 10-15 fold; in fact, a pregnant woman has more hormones in her body concurrently than a woman who never has kids will ever have over the entire span of her life.
This effect mirrors the gray matter reduction accompanied by hormonal increases during puberty. It’s counterintuitive, but the reduction in the gray matter actually results in a reorganization and specialization of the neural network, imbuing the new mother with a more acute ability to read emotional cues tacitly. So while the hormonal surge is meant to help the baby survive and grow to term in the womb, it also helps prepare the woman for motherhood and helps form the mother-child attachment, which in turn helps the baby survive after it’s been born.
In a 2-year follow-up to the first part of the study, the researchers did another brain scan of the mothers (those who did not have another child during that time period) and found the reduction in gray matter was still visible on the scan. Moreover, they were able to correctly identify with a high level of accuracy (95%) if a woman had had a child simply by looking at the image of her brain scan.
In the study they also took the brain scans of the fathers, using this as a measure of what happens to the brain of one who becomes a parent, but has not endured pregnancy. Their scans did not show any significant gray matter reduction, proving it really is the influx of hormones that is the catalyst of these enduring brain changes, not simply having a tiny human dependent on you for survival.
Another important take away from this study: the areas of gray matter decrease directly correlated to areas in control of mother-child attachment and decreased hostility to one’s baby. In lesser animals, this serves to keep the babies from being abandoned or cannibalized (yes, that does happen with some animals). In humans, we see these emotions materialize as post-partum depression (PPD) or a feeling of detachment from one’s child if they are not moderated. Women who did not have a significant reduction in gray matter during their pregnancy were more likely to have a lower level of mother-child attachment. Many women suffer from PPD and don’t understand why they feel this way. Imagine if you could know from a brain scan if you were more likely to suffer PPD? Knowing your susceptibility would make treatment and counseling so much easier and facilitate better post-partum care for the mother.
Now that we can visualize the changes that occur in the brain during pregnancy, we need to extrapolate that and perform further studies regarding the effect of taking hormonal birth control for years on brain structure. We know synthetic hormones can actually affect who you are attracted to, but what other parts of your brain can they effect? A woman’s natural hormone levels (estradiol and progesterone) decrease when supplemented with synthetic hormones, which can lead to a downstream increase in testosterone. What happens to the brain of these women who have a “masculinized” brain structure when they do become pregnant? Can their brain compensate or are they at a greater risk to be one of the women whose gray matter does not decrease as it should, putting them at a greater risk for PPD? Hopefully, researchers will keep looking into these long-term brain studies and give us answers to these questions.