Pregnancy changes brain structure
Brain researcher Elseline Hoekzema has discovered that the structure of the brain changes during pregnancy, particularly those areas related to social functions. These changes persist for at least two years after the mother gives birth. Publication in Nature Neuroscience on 19 December.
Long-lasting changes
Hoekzema’s research shows that during pregnancy strong and very consistent changes take place in the anatomy of the brain. The volume of the grey matter reduces, particularly in those areas that play a role in social cognition. Purely on the basis of these changes, a computer algorithm was able to recognize automatically whether or not a woman was pregnant. Follow-up research showed that these changes persist for at least two years after the birth. The researchers also demonstrate that there is a strong overlap with the network subserving Theory of Mind, a process that involves attributing mental states to oneself and others.
Becoming a mother
Hoekzema presumes that such changes in the brain may facilitate the transition to motherhood. ‘We found, for example, that the brain areas that changes during pregnancy coincide in part with those areas in a woman’s brain that exhibit the strongest response to her child in the period after the birth. Another finding was that certain measures mother-child bonding could be predicted on the basis of the structural changes in the grey matter of the brain.’
Comparison with adolescence
We know that sex hormones have a regulatory effect on for instance neuronal morphology, and it has previously been demonstrated that much smaller changes in these hormones can have effects on brain anatomy and brain function. Hoekzema: ‘It is not surprising that the unparalleled changes in a woman’s hormone levels during pregnancy would lead to changes in brain structure.’ Another period of increases in sex steroid hormones and reductions in grey matter volume is adolescence. Hoekzema: ‘We suspect that, as in adolescence, these changes could - at least partially - reflect a selective fine-tuning of connections into a more specialized and efficient neural network’.
Aim of brain changes
Female rats that have had one or more nests show clear and prolonged improvements in spatial memory, finding food and catching prey. Hoekzema: ‘We can easily imagine that in humans other skills are more important in terms of caring for offspring. The observed brain changes might serve an adaptive purpose for imminent motherhood. Changes in these social brain areas could, for example, help the mother to better recognize the needs of her infant.’
Conducting research
Hoekzema and her colleagues studied the influence of pregnancy on the brain by examining the brains of women who wanted to become pregnant with their first child. These women were followed when they became pregnant and investigated again after their pregnancy. Hoekzema: ‘This approach allowed us to reliably examine changes in brain structure using each woman’s pre-pregnancy brain scan as her individual baseline.’ The study also included several control groups, such as women who were not pregnant between the sessions, fathers and a control group made up of males. Hoekzema and her colleagues set up and conducted the study at the Universitat Autònoma de Barcelona in collaborationwith the fertility clinic Instituto Valenciano de Infertilidad. She completed the paper after transferring to Leiden University.
Not previously studied
Pregnancy involves unparalleled hormone increases and radical biological adaptations in a woman’s body. However, the effects of pregnancy on the human brain were virtually unknown. In non-human animals, it has been well established that reproduction leads to long-lasting changes in behaviour and in the brain. This is more difficult to investigate in humans, and very little research had been performed on this topic.
Pregnancy on the brain
Elseline Hoekzema, Erika Barba-Müller, Cristina Pozzobon, Marisol Picado, Florencio Lucco, David García-García, Juan Carlos Soliva, Adolf Tobeña, Manuel Desco, Eveline A Crone, Agustín Ballesteros, Susanna Carmona and Oscar Vilarroya
Nature Neuroscience: Pregnancy leads to long-lasting changes in human brain structure