Pregnant mothers-to-be avoid CT or X-ray examinations during pregnancy, and even some women who are planning to get pregnant are instructed not to get pregnant for six months after undergoing medical imaging because these high doses of radiation can deform the fetus. In fact, it depends on the size of the fetus how much the so-called high dose radiation affects the fetus, and it is analyzed stage by stage. Radiation has a threshold effects (threshold effects) this concept, refers to the dose below this, as not harmful to the human body, beyond the threshold, the severity and dose is proportional. Scientific research generally believes that the threshold of the fetus to produce intellectual effects is 0.2-0.4Gy; 0.05Gy or less will not abort, teratogenic or affect intelligence. As the fetus grows, increasingly higher doses of radiation are required to produce adverse effects. What is the concept of 0.05Gy? According to North American medical diagnostic X-ray or CT data, the highest radiation dose is for abdominal and pelvic CT, and even then it is only 0.01Sv, so 0.05Gy is very difficult to overcome. If a mother-to-be takes an ankle X-ray, the radiation dose is equivalent to standing for three more hours in daily background radiation, which is almost negligible. More importantly, the quality of life and mood of the mother-to-be is also important, and considering the small risk of radiation, necessary treatment and diagnosis should still not be avoided. Can CT or X-ray examinations during pregnancy cause fetal malformations? Even some women who are planning to get pregnant have been advised not to get pregnant for six months after undergoing medical imaging because these high doses of radiation can cause fetal malformations. In fact, the impact of the so-called high dose radiation on the fetus depends on the size of the fetus and is analyzed stage by stage. The fertilized egg is a single cell, if the radiation is particularly violent, it is almost impossible to produce only a single abnormality, the result is often catastrophic, that is, abortion; with cell division, to organogenesis before, this small group are all-powerful stem cells, if a serious injury or paroxysmal death, the adjacent can replace, is also unlikely to cause malformations. Therefore, scientists have imaginatively called this period “all-or-none period”. In other words, just one or two weeks after conception (i.e. 3 and 4 weeks of pregnancy), the mother-to-be will go for CT or X-ray, in case of harm, basically abort, otherwise the pregnancy will continue normally. Scientists have also found through rat experiments that the threshold for the most likely to be killed by radiation and cause abortion before fertilization of the egg and organogenesis is 0.15-0.2Gy, less than this value is fine. As long as the baby mice survive, they are strong and will grow normally. One cannot do experiments, but one can analyze historical disasters. After the accident at the Chernobyl nuclear power plant, the abortion rate increased in the Soviet Union. In farther central and northern Europe, such as Norway, Sweden, Finland, and Austria, there was no significant change in the rate of various reproductive defects, including malformations, stillbirths, and spontaneous abortions. Unfortunately, in some countries in southeastern Europe, some poor pregnant women were then persuaded to have abortions. Can X-rays cause fetal retardation? This is actually one of the concerns of the mothers-to-be. It is indeed difficult to mend nerve cells after they are damaged during the critical period of brain (including optic nerve) development. Scientists analyzed the Hiroshima and Nagasaki “little boy” and “fat” after the atomic bombing of pregnant women, once again confirmed that the maximum impact of radiation on intellectual development occurs in the 8-15 weeks of pregnancy, in this period of fetal, when the amount of radiation exposure to 1 Gy When the radiation exposure reaches 1Gy, 40% of the babies’ intelligence decreases, and when the radiation exposure increases to 1.5Gy, this percentage increases to 60%. At the time of radiation exposure, there were no significant mental deficits in fetuses less than 8 weeks and after 25 weeks. As already mentioned, the threshold of radiation for fetal intelligence is 0.2-0.4 Gy, and the results of this study were also derived from this experimental analysis. However, scientists also found that small amounts of radiation of 0.01-0.1Gy had no effect on fetal intelligence. We usually take a film or CT radiation dose of even 0.1Gy is very difficult to appear, so the film teratogenic actually not so easy. Unless you take X-rays every day, even so, scientists have verified through mice and rats experiments that even with a 0.2Gy dose of radiation for 1 hour a day for 10 and 11 generations, the experimental animals did not show reproductive and developmental defects. Can radiation cause leukemia in children? In 2001, scientists reviewed more than 650 cases of leukemia that occurred in Sweden between 1973 and 1989 to see how many of their mothers had had X-rays taken during pregnancy. It turned out that the fact that the mother had X-rays did not change the probability of leukemia in the child. In another study, the researchers divided the survey into pre-pregnancy couples who had X-rays and mothers-to-be who had X-rays for discussion, and found that these were not linked to whether the baby had leukemia. Of the 3,300 fetuses conceived after being exposed to radiation in two atomic bombings in World War II, only one died of leukemia or cancer 15 years after they were born. Tens of thousands of infertile men and women who were also exposed to radiation were no more likely to develop leukemia in their offspring. There are those in the scientific community who hold the opposite opinion, with one study claiming that abdominal x-rays taken during pregnancy increase the incidence of leukemia in babies by 50 percent. This may seem alarming, but it is important to know that the incidence of leukemia itself is extremely low. Some of the factors that increase the risk of leukemia that you wouldn’t even think of are the economic and social status of the parents, the amount of protein consumed by the child, and the birth weight of the newborn …… Down’s children are 10-20 times more likely to develop leukemia than other children. Nowadays, many families do not go for Down’s syndrome screening or even major teratology tests to avoid being frightened. Instead of worrying about the nebulous risk of that one or two x-rays, it is better to listen to your doctor and avoid the higher probability risks. Indirect harm is not easy either Some people ask if radiation can be harmful to the mother and indirectly affect the fetus? Scientists opened the rat mother’s abdomen at first conception, day 9 of gestation (equivalent to 3 weeks of human pregnancy, before organogenesis) and day 12 of gestation (early organogenesis), shielded the uterus and fetus with a lead plate, and gave the rat mother a mega-dose of 4 Gy of radiation; the protected rat embryos were exposed to only 0.01 Gy of radiation. As a control, some mouse embryos were irradiated directly with 4Gy and, of course, they all died. But in the case where the rat babies were protected, all of them were safe. Unless the mother rat is given more radiation to 10-14Gy, then even the mother dies. Based on the results of this experiment, we can at least speculate that it is difficult to affect the fetus if the mother-to-be takes an X-ray of the head, neck, chest or limbs once during pregnancy, if the abdomen is well protected. However, if a particularly large amount of radiation must be used for treatment, it is possible to damage the mother-to-be’s body, which in turn affects the fetus.