When is the embryo/fetus most sensitive to radiation exposure?

The embryo and fetus are most sensitive to radiation exposure during the first trimester of pregnancy, particularly in the early weeks after conception. During this period, critical processes such as cell division, organogenesis, and the development of the central nervous system are taking place. Rapid growth and differentiation of cells make the developing embryo particularly vulnerable to the damaging effects of radiation.

Exposure to radiation during this stage can lead to a variety of adverse effects, including developmental abnormalities, increased risk of cancer, and even miscarriage. As the pregnancy progresses, particularly in the second and third trimesters, the embryo has developed more fully and may be less susceptible to certain types of radiation damage, although caution should still be exercised throughout the entire pregnancy. This is why understanding the stages of fetal development and the associated risks is essential when managing radiation exposure in pregnant individuals.