Valeria Rosas

Structured Abstract Objective: Although the cranium and brain both grow rapidly during fetal development, tools for visualizing fetal skull separately from the brain have been limited. With increasing availability of fetal magnetic resonance imaging (MRI), we aimed to determine its feasibility for measuring cranial development and characterize how cranial and brain develop across gestation. Methods: This secondary analysis used MRI data from 50 pregnant women with singleton, typically developing pregnancies from 24 to 38.42 weeks’ gestation, collected as part of a longitudinal study of fetal and placental development. Biparietal (BPD) and occipitofrontal (OFD) diameters of the cranium and brain were manually delineated using standard software. Head circumference (HC) was calculated as HC = 1.62*(BPD + OFD), and cephalic index (CI) as CI = (BPD/OFD)*100. Total brain volume was determined as published previously.19 Manual segmentation of the fetal cranium was completed across gestation, and linear regression modeled relations between fetal skull measurements and brain volume. Results: Cranial measurements were successfully obtained from fetal MRI, demonstrating the feasibility of reliably delineating skull BPD and OFD across gestation. BPD ranged from 46.96-94.84mm and OFD ranged from 70.19-113.5mm. Total brain volume showed a positive linear relationship with head circumference, indicating MRI-based cranial measures track brain growth. Cephalic index wasn’t associated with brain volume and did not change with gestational age. Conclusions: Our study demonstrates MRI effectively distinguishes cranial and brain development during the fetal period. Head circumference reflects brain volume, whereas cephalic index does not. Differentiating skull and brain development enhances understanding of fetal neurodevelopment and supports improved prenatal monitoring.

Background: Neurodevelopmental outcome disparities, partially linked to socioeconomic status, race‐ethnicity, persist in congenital heart disease (CHD). Fetal brain development is a key predictor of subsequent neurocognitive outcomes. Methods: Magnetic resonance imaging was performed on fetuses with and without complex CHD at 2 sites. Childhood Opportunity Index (COI) and maternal race‐ethnicity were used to assess neighborhood and individual‐level maternal social determinants of health, respectively. The contributions of COI and race‐ethnicity on fetal brain volume, controlling for fetal gestational age and sex, were compared using multivariable regression between both groups. Results: Among 168 fetuses in this analysis, 106 (63.10%) were from non‐Hispanic White mothers, 43 (25.60%) were from Hispanic mothers, and 19 (11.31%) were from non‐Hispanic Black mothers. Total brain volume in the group with CHD (n=49) was significantly associated with the interaction of maternal race‐ethnicity and the COI Social and Economic subdomain Score (β=−0.74, P P =0.04). Maternal race‐ethnicity, COI Social and Economic subdomain Score, and their interaction accounted for 30% of the variance in total fetal brain volume in the group with CHD, although the same effect was not noted in the control group. Conclusions: Results indicate that maternal COI likely modifies the relationship between maternal race‐ethnicity and fetal brain development in CHD. The impact of maternal race‐ethnicity and COI on brain development differs between fetuses with and without CHD. Addressing maternal social determinants of health could reduce disparities in neurodevelopmental outcomes in CHD. Although limitations in sample size temper conclusions, initial analysis suggests that maternal social determinants of health and environment can contribute to neurodevelopmental outcome variance in individuals with CHD.