Question

Which changes take place during the first trimester of embryo development?

Answer 1

The first trimester, covering the first three months, is a period of rapid cell division, differentiation and organ formation.

1. During the first month, the embryo’s heart forms; its heartbeat can be detected early in development.
2. By about the end of the second month, limbs and digits develop, including fingers and toes.
3. By the end of the third month, major organs and organ systems, including the brain, liver, kidneys and intestines, are formed or developing substantially. Limbs and external genitalia are well developed; tooth buds and nails begin to form.
4. The basic body plan is established. Because organ formation is occurring, the embryo is especially vulnerable to harmful infections and teratogens.