This document discusses rules for minimizing radiation exposure during pregnancy, including the 10-day rule, 14-day rule, and 28-day rule. The 10-day rule, established in 1970 by ICRP, states that radiological exams of the lower abdomen and pelvis should be confined to the 10-day period following a woman's last menstrual period due to increased risk to the fetus in the first trimester. The 14-day rule restricts non-urgent pelvic x-rays to the first 14 days of the menstrual cycle. The 28-day rule, from 1984, says radiological exams can occur throughout the cycle until a period is missed, at which point the possibility of pregnancy should be considered. The document