Neuroimaging reveals traces of childbirth in the maternal brain
by PNAS:Pregnancy is one of the most dynamic periods in a woman’s life, involving a remarkable potential for brain plasticity that promotes cognitive and emotional adjustments to the newborn.A population-based neuroimaging study provides evidence for a relationship between number of childbirths and brain aging in 12,021 middle-aged women, suggesting that potential parity-related brain changes may endure beyond the postpartum period and influence the course of neurobiological aging.Maternal brain adaptations have been found across pregnancy and postpartum, but little is known about the long-term effects of parity on the maternal brain. Using neuroimaging and machine learning, the researchers investigated structural brain characteristics in the middle-aged women from the UK Biobank, demonstrating that parous women showed less evidence of brain aging compared to their nulliparous peers.The relationship between childbirths and a “younger-looking” brain could not be explained by common genetic variation or relevant confounders. Although prospective longitudinal studies are needed, the results suggest that parity may involve neural changes that could influence women’s brain aging later in life.
Summarized, the results show that parity can be linked to women’s brain age in midlife, in line with a recent analysis that tested for associations between brain age and a range of phenotypes in the UK Biobank. The researchers found no evidence that common polygenetic variation or confound variables could fully explain the differences in brain age gap between parous and nulliparous women.
Although prospective longitudinal studies are needed to conclude, the findings suggest that parity may involve long-lasting neural changes that could influence brain aging later in life and that such effects may be more prominent following multiple childbirths.
While the present results demonstrated a negative linear relationship between parity and brain age gap, follow-up analyses also showed evidence for a moderate quadratic effect , suggesting that any protective effects of parity may level off and be less pronounced in grand-parous (>5 births) women.
In line with this observation, parity has been linked to risk of Alzheimer’s disease (AD), with a higher risk in women with 5 or more completed pregnancies. Recent studies have also shown a J-shaped relationship between parity and mortality, with longevity peaking at 3 to 4 births.
Nulliparity has been associated with increased risk of autoimmune conditions, while grand multiparity has been linked to cardiovascular diseases including stroke and associated risk factors such as adiposity and diabetes.
Although it is possible that moderate-level parity could be more beneficial for brain agingrelative to nulliparity and grand multiparity, such effects could also be driven by other variables not considered, for example differences in socioeconomic factors or stress levels.
More studies controlling for relevant confounding factors are needed to fully understand the nature of the relationship between parity and brain aging.