Pregnancy causes changes in the brain to promote bonding with children, according to studies

Pregnancy is full of changes for women. And neurons are not immune to them. What does the latest research say about hormones, the brain, and motherhood?
Pregnancy causes changes in the brain to promote bonding with children, according to studies

In the eternal discussion about the existence or not of the maternal instinct, there are contributions from medicine, psychology and philosophy. Recently, a study from the Netherlands seems to confirm that the brain goes through changes with pregnancy to facilitate the care of children, strengthen the bond and facilitate tasks that have to do with parenting.

Elseline Hoekzema, leader of the research published this week in Nature, has been doing science on the brains of pregnant women for more than 10 years. As she herself stated in various statements, we do not have as much information as we would like about the neural modifications that happen in a pregnant woman.

Now, what are these changes in the brain during pregnancy about? Do they fulfill any social or survival function of the species?

Speculation about the results goes beyond biology. Could love for children be programmed into our species? We analyze it.

Research in the Netherlands: what was it about?

Hoekzema’s team had 89 young women from their country who agreed to participate in the long-term research since 2015. All of them were nulliparous, that is, they had no previous births.

After 5 years, in 2020, 40 had had a child. Another 40 who had not been mothers served as a control group for the studies. The remaining 9 abandoned their participation.

The scientists analyzed the women’s brains with MRIs and imaging scans before they conceived, after giving birth in all 40 who had become pregnant and a year after childbirth in 28 of them. The 40 non-pregnant women in this span were also studied to have a benchmark.

In addition to the resonances, intelligence and cognitive performance tests were performed. In pregnant women, hormone levels in the urine were measured regularly.

MRI provides images without emitting radiation, making it safe for breastfeeding women.

The results

This same scientific work team had published a preliminary study in 2017. There they already reported findings that showed a significant change in the gray matter of the brain of women who became pregnant.

Now, several years later, the results are repeated. At both times, MRIs showed a reduction in gray matter after pregnancy. This substance is the accumulation of the bodies of neurons in the central nervous system.

But the reduction does not mean a loss of functions. On the contrary, scientists explain that changes in the brain during pregnancy are the signal that hormones remodel the mother’s nervous system.

A similar modification occurs when a woman goes through adolescence. That is, when hormone levels also oscillate abruptly

We believe that the reduction is due to a process similar to synaptic pruning that takes place during adolescence, when weak synapses are removed to favor more mature and efficient mental processing.

Susanna Carmona, leader of the neuromaternal group at the Gregorio Marañón Hospital ~

What had been the contributions of 2017?

The new research adds to the 2017 findings of this research group. At that time, the most relevant thing that had been discovered was the following:

  • Most of the changes are focused on the region known as the nucleus accumbens. Thus, the mother is more attracted to the baby’s stimuli.
  • The mother’s prefrontal cortex is modified to identify her child’s cry. This same change stimulates pleasurable sensations when the woman sees her baby smile.

The brain changes in pregnancy to worry about the other

The research team supplemented analyses in the participating women with functional magnetic resonance imaging. This is an imaging study that records the activity of neurons as the brain “works.”

With this, they were able to observe that changes in gray matter were concentrated in neural networks dedicated to self-reflection and socialization. This could mean that modifications tend to improve interrelation with others, empathy, bonds. Something that seems essential for the care of a child.

The result is reinforced by other data collected in this group of mothers. The researchers showed the women photographs of smiling babies and found a reduction in heart rate in several of them. This decrease in pulsations is noticeable when we enter states of relaxation.

In women with more changes in the MRI there was greater reduction in pulsations. So it is inferred that the remodeling of the gray matter results in a high possibility of producing a satisfactory bond with a baby.

And there are long-term effects.

Changes in the brain during pregnancy also appear to have a long-term effect. While modifications tend to disappear within 2 years of birth, there would be consequences that science fails to fully elucidate.

This goes beyond popular sayings that say that pregnant women are more clueless. Although that data has been corroborated in Australia, where a small investigation found a slight deterioration in the daily memory of women who had just become mothers.

Studies found that having more pregnancies increases the risk of Alzheimer’s later in life. However, these same reviews indicate that the data are inconclusive. It does seem clear that women who went through difficult pregnancies, with diabetes or high blood pressure, were more likely to age with aneurysms in the brain and, therefore, with a memory deficit because of it.

Estrogens would be protective against the decline of brain functions in old age. Studies suggest that hormonal variations in pregnancies would slow memory decline in women.

Although here the question is not so clear because menopause also makes its own. So, it is not yet possible to assess which stage has more influence on the brain of the elderly.

Are changes due to pregnancy or those derived from the climacteric more important?

Is there a maternal instinct for science?

This research in the Netherlands adds to several attempts by science to reveal what lies behind the maternal instinct. Or in any case, answer the question about the existence of such an instinct.

Feldman established in 2015 that the brain of mammals (including humans) changes for motherhood. Specifically, there are modifications in the reward circuit, which regulates satisfactions against various stimuli. The two organs most involved here are the amygdala and hypothalamus.

Oxytocin, a hormone involved in pregnancy, childbirth and lactation, modifies brain biochemistry to promote the mother-child bond. And there’s more. One study found that levels of this substance also increased in males who fathered and made skin-to-skin contact with their children from the get-go.

Regarding boys, an international sample also recorded changes in the gray matter of the brains of those who were fathers. Not at the same level as women in the Netherlands or in the same locations.

Changes in the brain from pregnancy occur a lot at a subcortical level, below the cortex. This area is more primitive in evolution and could indicate an adaptation that we inherited from our hominid and mammalian ancestors. In males, the changes are restricted to the cortex.

The brain does not change the same in women who are mothers and in men who are fathers.

Is the maternal instinct inevitable?

The existence of this primitive and inherited mechanism of change in the brain by pregnancy cannot be directly associated with the maternal instinct. Sara Henderson’s doctoral thesis covers all the biological and social aspects that make up what constitutes a supposed tendency of women to be mothers and take care of their children.

It is evident that pregnancy involves a lot of changes. Hormones exert effects that tend to preserve the new life that is gestation.

Our hypothesis is that pregnancy hormones, mainly steroids, are the main factor regulating the plasticity of neurons in pregnant women.

Conclusion of the study Nat Commun 13, 6931 (2022). ~

And it is very possible that these changes will last during the first years of the child’s existence. Why? Perhaps for the survival of the species.

Much remains to be discovered about pregnancy, mothers’ brains and their changes. What is the place of the maternal instinct in this game of relationships? We are still not sure.

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