by Pia Johansson
Science tells us that mothers react more to their own baby crying or laughing than to a control baby. Well, I guess you already knew that, but did you know that your brain changes in size and your reward circuits are rewired in preparation for and in adaptation to parenthood? And that fetal cells migrate to your brain?
There are significant changes in the maternal brain, all supposedly designed to support mothers in the demanding tasks of protecting and building strong relationships with their offspring. Magnetic resonance imaging (MRI) studies have shown that mothers react more to their own baby crying than to other babies. Any mother will say that this is hardly a ground-breaking discovery. This is true, but a bit more in-depth analysis can tell us a bit more about this phenomenon.
First, it has been found that the actual size of a mother’s brain decreases during pregnancy! The brain was smallest around the time of the baby’s birth and regained its size again postpartum. Interestingly, it also turns out that during the postnatal re-growth, areas involved in “parenting” increased more than “non-parenting” areas. Even though the purpose of this is not completely clear, it has been suggested to be akin to a rearranging or pruning of synapses and connections in preparation for the life-altering event of parenthood. New connections and synapses are formed after the baby is born. A similar pruning rearrangement has also been shown in the transition from teenager to adult. MRIs can also show us which areas are activated during certain tasks or situations. Three major circuits known to be involved in parenting showed increased activity in mothers: the reward and maternal motivation circuit (involved in many reward situations like food, drugs and sex), the social information circuit (involved in empathy, self-monitoring and reflection), and in the emotion regulating circuits (involved in regulation in negative emotional reactions).
What is regulating these changes? Well, this is quite complicated and not clear, but hormones definitely play a role. One study showed decreased performance in a recall memory task both during pregnancy, and postpartum (so it’s not just me!), and the extent of the deficiency could be predicted by prenatal levels of estrogen and glucocorticoids.
Another very interesting hormone in regard to all things motherhood is oxytocin. This is the hormone that is involved in inducing both uterine contractions during labour and milk production after. But interestingly, it also has central (i.e., nervous system) actions and seems to be involved in regulating a lot of maternal behaviour. Animal studies even show that administration in non-mothers induces maternal behaviour and blocking it suppresses such behaviour. In human mothers, it has been found that maladaptation to motherhood is at least partly linked with oxytocin dysregulation, however causality cannot be determined here. The oxytocin levels increase during pregnancy, which helps the mother in first reacting to the baby, then the interaction in the postpartum period further increases the oxytocin levels through the already more active and sensitised reward circuits, creating a beautiful mother-baby reward cycle.
On a side note, I had previously heard that oxytocin helps the mother forget the pain of childbirth, which to some explained why women would be willing to have more than one child. But this appears to be a myth, and maybe even partly the patriarchy at work, as there is no scientific research backing this up. Turns out that women are just really tough, and in the end pain is not all you get from giving birth; in the end you have a beautiful baby as well, making the whole experience more positive, even in extreme pain situations.
What is also interesting, but maybe of lesser functional relevance, is something called maternal-fetal microchimerism. This sounds complicated, but it means that cells from the baby have migrated into the mother and can be found in blood, as well as various organs, including the brain. This concept might already be familiar to some of you who have done fetal diagnostics in recent years. The discovery of fetal cells in the mother and in particular in maternal blood have really revolutionised fetal diagnostics. You can now, if desired, have chromosomal abnormality and other tests performed through a simple maternal blood test, without any risk to the baby. Anyway, what I wanted to say was that these cells that have migrated from the baby across the placenta into the mother, migrate into various tissues, including the brain, and can be found there decades after the baby is born. Now, the jury is still out on the purpose (if any) of this migration and whether the result of their presence is beneficial or not, but I think this is a little bit freaky, but also quite cool! A little part of them is always with us!
To sum it up, I find it interesting that it is clear, even to the brain, that becoming a parent is not a small thing. Indeed, the ability to change and rewire ones’ brain in order to care for, protect, and even socialize an infant would be considered an evolutionary adaptation that insures the survival and downstream reproduction of the offspring (i.e. if you look after your baby well, it not only survives, but also becomes a nice, happy human who can then reproduce and look after its own babies). The brain not only adapts in response to motherhood, but in preparation for it. Further, it is also clear that the peripartum period is a period with increased sensitivity and brain plasticity. The brains of expectant and new mothers are very susceptible to both negative and positive experiences. And this is where the sisterhood, the community of motherhood, comes into play. Let’s help each other, help and support new mothers. Everything positive helps to build a new, strong, positive, maternally rewired brain.
Pia Johansson is a research scientist in neurobiology, mother of two and working mum. She was an expat for almost twenty years, in Australia and Munich and a short wild stint in Dublin many many years ago. She is in the throes of being repatriated to Sweden with her Australian husband. She likes talking, running and talking about running. And chocolate (although mostly 85% these days, as crazy as that sounds). In addition to staying fit and eating healthy, and raising happy healthy children, she dreams of doing something a little bit creative like writing or becoming a photographer. Or at least organizing her photos soon.