X-rays should be avoided as much as possible in early pregnancy, especially in the first 3 months of pregnancy. Routine chest X-rays can be postponed until 6-7 months. Gastrointestinal imaging and barium enemas that require longer irradiation should be avoided as much as possible. After 36 weeks of gestation, if obstetric conditions require X-ray radiographs, one X-ray examination has little effect because the fetus is basically mature at this time. Some pregnant women do not know they are pregnant in the early stages of pregnancy and undergo X-rays. There is no need to be overly alarmed and they can go to the obstetrical genetic counseling clinic to decide whether to continue the pregnancy. In addition, diagnostic treatment with radioisotopes is becoming increasingly widespread in clinical practice. Although the half-life of these elements is relatively short, it can enter the fetus through the placental blood circulation. 125I (iodine-125) and 131I (iodine-131) used in the past are now mostly not used in order to avoid the impact on fetal development. At present, 113In (Indium-131) is used clinically to diagnose placenta praevia and other diseases because of its short half-life and low impact on pregnant women and fetuses. The maximum safe exposure for a normal person in one radiological examination is 2.58×10-2 cu/kg. Generally speaking, the total cumulative time for chest fluoroscopy within a week does not exceed 12 minutes, and gastrointestinal examination does not exceed 10 minutes, which is safe for human body. Although the exposure dose of X-ray radiography is higher, an occasional radiography or X-ray fluoroscopy is not harmful to health. However, women of childbearing age, especially pregnant women, whose eggs, embryos or fetuses are highly sensitive to radiation, can cause damage to the mother and fetus even if the radiation dose is significantly lower than what a normal person can tolerate. Therefore, pregnant women should avoid radiological examinations.