What type of abnormality can be expected in a baby if the mother is irradiated during the third trimester of pregnancy?

When considering the effects of maternal irradiation during the third trimester of pregnancy, the potential for malignant diseases in the baby is a serious concern. The third trimester is a critical period for fetal development, although the major organ systems have already developed by this time. Exposure to ionizing radiation can lead to somatic mutations that may not become apparent until later in life, manifesting as various types of cancers.

While other options may also represent potential risks of exposure, studies and data on the effects of radiation have indicated a stronger correlation between significant radiation exposure in the later stages of pregnancy and an increased risk of cancers such as leukemia in the offspring. The biological mechanisms involve the ionization of cellular components which can disrupt normal cellular processes, leading to malignancies.

Thus, the focus on malignant diseases as a potential outcome reflects well-documented concerns in medical literature regarding the long-term effects of radiation exposure on developing fetuses, particularly in the context of significant radiation doses.