Organogenesis occurs in which pregnancy period?

• A. Pre-implantation period
• B. Organogenesis period
• C. Fetal period
• D. Postnatal period

Answer: (B)

Organogenesis is the stage when the body’s organs start to form from the three germ layers, and it happens during the embryonic period of pregnancy. In humans, this occurs roughly from week 3 to week 8 after fertilization. That timing is why organogenesis is the correct period: it’s the window when organ primordia are established and first patterned. Before this window, development is the pre-implantation phase, focused on implantation and early cell divisions; after this window, the fetal period involves growth and maturation of already formed organs, not their initial formation; and postnatal is after birth.