Summary: New research indicates that conditions in the womb can shape adolescent brain development, influencing cognitive processing and emotional regulation.
Source: Concordia University.
Factors such as fetal position and nutrition influence cortical development
Recent research shows that variations in the prenatal environment can leave lasting marks on brain development that are detectable in the teenage years. A team of Quebec-based researchers reports that differences in the in utero experience are associated with measurable changes in cortical structure—changes that may affect both emotion regulation and cognitive abilities.
Published in Human Brain Mapping, the study was led by Linda Booij, an associate professor of psychology at Concordia University and a researcher at Sainte-Justine Hospital Research Center. The team followed pairs of genetically identical (monozygotic) twins from birth into adolescence to isolate the impact of non-genetic prenatal influences.
Study design: identical twins reveal prenatal effects
Because monozygotic twins share the same genetic code, comparing them provides a powerful way to detect environmental influences that act before birth. The researchers tracked birth weight differences within twin pairs as an indicator of distinct prenatal experiences. Birth weight discordance can reflect factors like relative fetal placement in the womb or unequal access to nutrients during pregnancy.
By focusing on twins with different birth weights, the investigators could examine whether those early, non-shared conditions were linked to differences in cortical anatomy during adolescence. The team collected brain imaging and DNA samples from a subgroup of the cohort to explore both structural and epigenetic correlates.
Size matters: birth weight and cortical anatomy
The study found that, within twin pairs, the sibling with the higher birth weight tended to have a larger total cortical surface area and increased cortical volume, while showing decreased cortical thickness compared with their lower birth weight co-twin. These associations indicate that differences in the prenatal environment—reflected by birth weight discordance—are related to variations in cortical morphology that persist into the teen years.
Because the twins are genetically identical, these structural differences cannot be attributed to inherited genetic variation. Instead, they point to prenatal environmental factors as key drivers of early brain development.
Epigenetics and brain outcomes
In addition to structural MRI, the researchers measured DNA methylation patterns from saliva samples taken at age 15. DNA methylation is an epigenetic mechanism that can alter how genes are expressed in response to environmental influences without changing the underlying genetic code.
Twin pairs with larger differences in birth weight and cortical structure also showed greater differences in DNA methylation. That pattern suggests epigenetic processes may mediate the relationship between prenatal conditions and later cortical development. The investigators identified candidate genes related to neurodevelopment that could help explain how birth weight discordance translates into differences in cortical volume and surface area.
Overall, the findings support the view that the prenatal environment shapes brain structure in ways that are detectable during adolescence, and that epigenetic mechanisms likely play a role in this developmental cascade.
Lead author Linda Booij and collaborators emphasize that these results help clarify how early environmental differences can influence brain anatomy and gene expression patterns relevant to emotional and cognitive outcomes. By pinpointing prenatal influences and possible epigenetic mediators, the work aims to inform strategies that support healthy brain development and reduce the risk of emotional or cognitive problems in youth.
Authors: Kevin F. Casey, Melissa L. Levesque, Moshe Szyf, Elmira Ismaylova, Marie-Pier Verner, Matthew Suderman, Frank Vitaro, Mara Brendgen, Ginette Dionne, Michel Boivin, Richard E. Tremblay, Linda Booij.
Funding: The research was supported by Sainte-Justine Hospital, the Canadian Institutes of Health Research, the Fonds de recherche du Québec-Santé, the Canada Research Chair program, the Fonds Québecois de la Recherche sur la Société et la Culture, the Social Science and Humanities Research Council of Canada, the National Health Research Development Program, Université Laval and Université de Montréal.
Abstract (condensed)
Background: Prior studies have linked birth weight, a proxy for the in utero environment, to cortical morphology in later life. Monozygotic twin designs suggest non-shared prenatal factors drive this association. The present study tested whether differences in DNA methylation mediate the relationship between birth weight discordance and cortical structure.
Methods: The team assessed 104 adolescent monozygotic twins (52 pairs) using T1-weighted structural MRI and an epigenome-wide analysis of DNA methylation from saliva at age 15.
Results: Twins were similar overall, yet higher birth weight co-twins showed greater cortical surface area and volume and reduced cortical thickness relative to their lower birth weight siblings. Birth weight discordance correlated positively with cortical surface area and volume discordance. Preliminary analyses identified neurodevelopment-related genes as potential mediators of the observed relationships.
Conclusions: Findings indicate that prenatal environmental differences contribute to adolescent cortical morphology and that DNA methylation may help explain how birth weight differences influence brain development.
Original study: “Birth weight discordance, DNA methylation, and cortical morphology of adolescent monozygotic twins” published in Human Brain Mapping. Published online December 29, 2016. DOI: 10.1002/hbm.23503.