During which trimester does organogenesis occur?

Organogenesis is the process during embryonic development in which the major organs and structures of the organism begin to form. This critical phase occurs during the first trimester of pregnancy, specifically from weeks 3 to 8. During this period, the embryo undergoes significant transformation, establishing the foundational elements of the heart, brain, limbs, and other essential systems.

The first trimester encompasses the initial stages of conception and key developmental milestones that set the stage for further growth. By the end of this trimester, the developing fetus has established most of its internal organs, making this stage crucial for proper development. Subsequently, the second and third trimesters are periods mainly dedicated to growth and maturation of these already formed organs and systems, rather than their initial development. Therefore, the correct response is that organogenesis primarily occurs during the first trimester.