Fetal corpus callosum growth patterns mapped from 18 to 32 weeks

Researchers analyzed 3D fetal brain volumes from 956 singleton pregnancies at two centers in Hong Kong and Japan. The study included prospectively acquired and archived scans of appropriately grown fetuses without suspected structural or chromosomal abnormalities, imaged at 18–32 weeks’ gestation. They measured corpus callosum (CC) length and total area, thickness at the genu, body and splenium, and areas of five subdivisions. Measurements made with and without volume contrast imaging (VCI) were compared, and gestational-age-specific growth curves were modeled.

CC measurements followed distinct, nonlinear trajectories. Genu and body thickness increased sharply from 18 to 23 weeks; genu thickness then rose gradually, while body thickness plateaued before renewed growth at 31–32 weeks. Total CC area increased steadily. The splenium had the greatest absolute area growth, reaching a median of about 0.40 cm² by 32 weeks. Measurements were comparable between VCI and non-VCI modes and generally showed good-to-excellent reproducibility, although interobserver reliability was moderate for genu and body thickness.

The findings describe normal regional development in the studied gestational range. The authors caution that the clinical significance of regional measurements is uncertain and that these trajectories should not be used alone for clinical decisions. Their prognostic value requires longitudinal studies with postnatal neurodevelopmental assessment.