From the Guidelines
The brain development in a fetus begins around the fifth to sixth gestational week, with the proliferation of neurons in the dorsal telencephalon, and continues to develop and mature throughout the gestational period, with significant growth and refinement occurring during the second and third trimesters.
Key Stages of Brain Development
- The proliferation of neurons in the dorsal telencephalon of the human fetus begins around the fifth to sixth gestational week, decreases after 16 gestational weeks, and finishes around 22–25 gestational weeks 1.
- The migration of neurons begins at a time when the first neurons are formed (around fifth to sixth gestational week), peaks between the third and fifth months of gestation, and ends around 30–35 gestational weeks 1.
- The cerebral cortex develops its characteristic folded appearance during the second trimester, with the outer subventricular zone (oSVZ) playing a crucial role in the expansion and gyrification of the primate/human cortex 1.
Importance of Prenatal Care
The extended developmental timeline of the brain makes it particularly vulnerable to disruptions throughout pregnancy, highlighting the importance of proper prenatal care, nutrition, and avoiding harmful substances for healthy brain development.
Critical Periods of Brain Growth
The second trimester (weeks 13-26) is a critical period of rapid brain growth, with neurons forming and migrating to their proper locations, while the third trimester (weeks 27-40) is marked by significant brain growth and refinement, with the brain nearly tripling in weight and synaptic connections forming extensively 1.
From the Research
Fetal Brain Development
The development of the brain in a fetus is a complex process that involves multiple stages.
- Neural tube formation is a critical step in the development of the brain and spinal cord, and it occurs early in fetal development 2, 3.
- In humans, the neural plate converts into a tube by the fourth week of pregnancy, and failure of this process can lead to neural tube defects (NTDs) 2.
- The signaling mechanisms governing neural tube morphogenesis are unclear, but studies have shown that vesicular glutamate release is necessary for neural tube formation 2.
- Neural tube closure is critical for the formation of the human brain and spinal cord, and it is influenced by a complex interplay of genetic, environmental, and epigenetic factors 4.
Timeline of Brain Development
- The neural tube forms during the fourth week of pregnancy, and this marks the beginning of brain development 2.
- The neural tube then undergoes a series of complex morphogenetic events, including folding, bending, and closure, to form the brain and spinal cord 3.
- Ion channels play a crucial role in neural development, including neural tube formation, neural cell proliferation, and neuronal differentiation 5.
- The development of the brain and spinal cord is a highly regulated process that involves the coordinated action of multiple cellular and molecular mechanisms 6, 4.