What occurs during the first trimester of pregnancy?

What occurs during the first trimester of pregnancy?

• A. Zygote develops into embryo and then early fetus
• B. Delivery occurs
• C. Growth of the fetus
• D. Embryo becomes placenta

Answer: (A)

During the first trimester the developing conceptus moves from fertilization through early development to a fetal stage. Fertilization creates a zygote, which undergoes rapid cell divisions and implants into the uterine lining. Once implanted, the structure is called an embryo. By the end of the first trimester, it has progressed toward a fetal stage, so the sequence zygote → embryo → early fetus accurately describes what happens in this period. Delivery occurs much later, after full term; growth of the fetus happens throughout pregnancy but the major milestones of the first trimester are these early developmental transitions and the start of organ formation. The placenta forms alongside the embryo rather than being something the embryo becomes.

During the first trimester the developing conceptus moves from fertilization through early development to a fetal stage. Fertilization creates a zygote, which undergoes rapid cell divisions and implants into the uterine lining. Once implanted, the structure is called an embryo. By the end of the first trimester, it has progressed toward a fetal stage, so the sequence zygote → embryo → early fetus accurately describes what happens in this period. Delivery occurs much later, after full term; growth of the fetus happens throughout pregnancy but the major milestones of the first trimester are these early developmental transitions and the start of organ formation. The placenta forms alongside the embryo rather than being something the embryo becomes.