During which period is the central nervous system most vulnerable to teratogenic effects?

The central nervous system is most vulnerable to teratogenic effects during the embryonic period. This phase, which spans from approximately week 3 to week 8 of gestation, is characterized by critical developments in the formation of the brain and spinal cord. During this time, the neural tube closes, and major brain structures begin to differentiate and mature.

Exposure to teratogens—substances or factors that can cause malformation of an embryo or fetus—during the embryonic period can lead to significant structural anomalies. This includes neural tube defects, microcephaly, and other developmental disorders, as the foundational neural architectures are being established. Although teratogenic effects can still occur later in pregnancy, the risk is notably higher during the early embryonic stage, which is pivotal for the proper formation of the central nervous system.

In contrast, during the fetal period, which ranges from week 9 until birth, the central nervous system undergoes maturation processes rather than formation, making it somewhat less susceptible to teratogenic effects at this later stage. The neonatal and postnatal periods involve post-birth development, where exposure to teratogens is unlikely to affect the structure of the central nervous system in the same way, although environmental factors can influence