In which portion of pregnancy is the embryo/fetus most radiosensitive?

In which portion of pregnancy is the embryo/fetus most radiosensitive?

• A. The first trimester
• B. The second trimester
• C. The third trimester
• D. Postpartum period

Answer: (A)

The embryo and fetus are most radiosensitive during the first trimester of pregnancy due to rapid cellular division and differentiation taking place. During this period, especially in the early weeks, the developing tissues are particularly vulnerable to the effects of radiation. The type of damage that can occur includes teratogenic effects, which can lead to congenital malformations, and even the potential for miscarriage.

The critical development occurring in the first trimester involves the formation of essential organs and structures, making the cells more susceptible to radiation-induced changes. As pregnancy progresses into the second and third trimesters, the developing fetus becomes less radiosensitive because the rate of cellular proliferation decreases and the tissues become more differentiated. Additionally, by the time of the postpartum period, the fetus has already been delivered and is no longer exposed to the conditions present during pregnancy.