Microscopic anatomy of human fetal precentral cerebral wall in the fetuses of the second trimester

The human fetal cerebral wall undergoes key laminar organisation during mid-gestation, forming the basis for cortical development. The precentral gyrus is a critical motor region where early disturbances may affect neurodevelopment. This study examined the transient cortical layers of the fetal precentral cerebral wall during the second trimester. After ethics approval, ten normal fetal brains between 18 and 25 gestational weeks were analysed. Precentral cerebral wall tissue was sectioned at 5 μm and stained with haematoxylin–eosin and Luxol Fast Blue/Periodic Acid–Schiff. Six transient layers—marginal zone (MZ), cortical plate (CP), subcortical plate (SCP), intermediate zone (IZ), subventricular zone (SVZ), and ventricular zone (VZ)—were identified and measured using CellSens software, and correlations with gestational age were assessed. Mean cerebral wall thickness was 5.5 ± 2.1 mm, with SCP and IZ consistently the thickest layers and VZ the thinnest. Significant positive correlations were observed between gestational age and both CP and SCP, as well as between MZ and CP, MZ and VZ, and SCP and IZ. Occasional specimens showed oedema in the SVZ and spongy IZ. These findings demonstrate that the second-trimester precentral cerebral wall exhibits six distinct transient layers with coordinated growth, particularly within the subplate and cortical plate, providing region-specific normative data that enhance anatomical understanding of cortical development during a critical developmental window.