Thyroid nodules after prenatal exposure to chernobyl radioactive fallout in Belarus

The significant risk of thyroid nodules associated with exposure in the third trimester indicates the presence of a vulnerable subgroup of pregnant women at the time of an accidental radioiodine release. Because of the strong correlation between gestational age and 131I dose in the fetal thyroid, the extent to which this excess risk is attributable to elevated 131I dose and/or radiosensitivity of the thyroid in later stage of fetal development remains unclear.