Impact of Demographic and Obstetric Factors on Infant Brain Volumes: A Population Neuroscience Study

Abstract

Individual differences in neuroanatomy are associated with intellectual ability and psychiatric risk. Factors responsible for this variability remain poorly understood. We tested whether 17 major demographic and obstetric variables were associated with individual differences in brain volumes in 756 neonates assessed with MRI. Gestational age at MRI, sex, gestational age at birth, and birthweight were the most significant predictors, explaining 31% to 59% of variance. Unexpectedly, earlier born babies had larger brains than later born babies after adjusting for other predictors. Our results suggest earlier born children experience accelerated brain growth, either as a consequence of the richer sensory environment they experience outside the womb or in response to other factors associated with delivery. In the full sample, maternal and paternal education, maternal ethnicity, maternal smoking, and maternal psychiatric history showed marginal associations with brain volumes, whereas maternal age, paternal age, paternal ethnicity, paternal psychiatric history, and income did not. Effects of parental education and maternal ethnicity are partially mediated by differences in birthweight. Remaining effects may reflect differences in genetic variation or cultural capital. In particular late initiation of prenatal care could negatively impact brain development. Findings could inform public health policy aimed at optimizing child development.

Keywords: birthweight; neonate; neuroimaging; premature birth; socioeconomic status.

Figure 1.

Gestational age at MRI is strongly associated with GM volumes. Panel a: Multiple regression showed that gestational age at MRI has a strong, positive association with total GM volume in infancy (adjusted for birthweight, sex, gestational age at birth, and scanner). Panel b: DBM identifies associations between gestational age at MRI and local GM volumes (adjusting for birthweight, sex, gestational age at birth, scanner, and ICV). Positive associations, indicating fast-growing regions are shown in red and negative associations, indicating slow-growing regions are shown in blue. Significant clusters projected onto surface-rendered views of the left and right hemispheres; lateral view (top), medial view (bottom).

Figure 2.

Child sex is associated with GM volumes. Panel a: Multiple regression showed that males have larger total GM volume in infancy compared with females (adjusted for birthweight, gestational age at MRI, gestational age at birth, and scanner). Panel b: DBM identifies associations between sex and local GM volumes (adjusting for birthweight, gestational age at MRI, gestational age at birth, scanner, and ICV). Regions where females have relatively larger GM volumes are shown in red and regions where males have relatively larger GM volumes are shown in blue. Significant clusters projected onto surface-rendered views of the left and right hemispheres; lateral view (top), medial view (bottom).

Figure 3.

Birthweight is associated with GM volumes. Panel a: Multiple regression showed that birthweight has a positive association with total GM volume (adjusted for sex, gestational age at MRI, gestational age at birth, and scanner). Panel b: DBM identifies associations between birthweight and local GM volumes (adjusting for sex, gestational age at MRI, gestational age at birth, scanner, and ICV). Positive associations are shown in red and negative associations are shown in blue. Significant clusters projected onto surface-rendered views of the left and right hemispheres; lateral view (top), medial view (bottom).

Figure 4.

Gestational age at birth is associated with GM volumes. Panel a: Multiple regression showed that earlier born babies had larger total GM volume (adjusted for sex, gestational age at MRI, birthweight, and scanner). Panel b: DBM identifies associations between gestational age at birth and local GM volumes (adjusting for sex, gestational age at MRI, birthweight, scanner, and ICV). Panel c: DBM identifies associations between gestational age at birth and local GM volumes (adjusting for sex, days post-birth, birthweight, scanner, and ICV). Positive associations are shown in red and negative associations are shown in blue. Significant clusters projected onto surface-rendered views of the left and right hemispheres; lateral view (top), medial view (bottom).