Babies born in poverty have smaller brains than mothers in better positions, study finds

Environmental factors influence the structure and function of young brains before babies are even born, Washington University School of Medicine researchers have found. 

MRI scans performed on healthy newborns while they slept indicated that babies of mothers facing social disadvantages such as poverty tended to be born with smaller brains than babies whose mothers had higher household incomes.

Full-term newborns born to mothers living in poverty revealed smaller volumes across the entire brain, including the cortical gray matter, subcortical gray matter and white matter – than found in the brains of babies whose mothers had higher household incomes. 

The scans, conducted in the first weeks of life, also showed evidence of less folding of the brain among infants born to mothers living in poverty. Fewer and shallower folds typically signify brain immaturity. The healthy human brain folds as it grows and develops, providing the cerebral cortex with a larger functional surface area.

A second study of data from the same sample of 399 mothers and their babies found that pregnant mothers from neighborhoods with high crime rates gave birth to infants whose brains functioned differently during their first weeks of life than babies born to mothers living in safer neighborhoods.

Functional MRI scans of babies whose mothers were exposed to crime displayed weaker connections between brain structures that process emotions and structures that help regulate and control those emotions. Maternal stress is believed to be one of the reasons for the weaker connections in the babies’ brains.

“These studies demonstrate that a mother’s experiences during pregnancy can have a major impact on her infant’s brain development,” said Principal Investigator Dr Christopher D. Smyser. 

“Like that old song about how the ‘knee bone is connected to the shin bone,’ there’s a saying about the brain that ‘areas that fire together wire together.’ We’re analysing how brain regions develop and form early functional networks because how those structures develop and work together may have a major impact on long-term development and behaviour.”

Babies in the study were born from 2017 through 2020, before the start of the COVID-19 pandemic. 

“Social disadvantage affected the brain across many of its structures, but there were not significant effects that were related to psychosocial stress,” first author Dr Regina Triplett said. 

“Our concern is that as babies begin life with these smaller brain structures, their brains may not develop in as healthy a way as the brains of babies whose mothers lived in higher income households.”

Association of Prenatal Exposure to Early-Life Adversity With Neonatal Brain Volumes at Birth was published in JAMA Network Open, while The Effects of Prenatal Exposure to Neighborhood Crime on Neonatal Functional Connectivity was published in Biological Psychiatry.