Pregnant women are very worried about taking X-rays and often take X-rays without knowing they are pregnant. They were concerned about the safety of fetal radiation and demanded abortion. is it necessary?
careful! Radiation dose
Embryos exposed to ionizing radiation may cause embryonic death, miscarriage, fetal congenital malformations, mental retardation, cerebellar disease, and fetal growth retardation. These embryonic injuries are mainly related to radiation dose and embryonic development stage. It is possible to exceed the safe dose, which we call the threshold dose phenomenon.
As for the increased chance of developing childhood cancer or blood cancer in the future, it is generally considered to be a non-threshold dose phenomenon, which may theoretically be caused by radiation exposure, but it is generally believed that the dose must be higher than 20 rads. According to literature reports, if one sibling in the family suffers from leukemia, the probability of other siblings suffering from leukemia is 1:720, which is much higher than the potential cancer risk of 1:6000 from radiological diagnosis.
Usually in the early stages of pregnancy, that is, before the embryo implants or before the organ development period (1-14 days of pregnancy), the embryo will not be damaged by ionizing radiation during this period. This period of early embryonic development is an all-or-nothing injury phenomenon. According to animal experiments, the radiation dose must be greater than 1.5-2.0 Gy to cause embryonic death. If the fetus does not die and the fetus continues to develop, the risk of congenital malformations is the same as for a normal embryo.
The most sensitive period for radiation damage
The most sensitive period for embryonic development to radiation damage is 22 days after conception. The radiation dose at this time must be higher than 20 rads to cause congenital malformations in the embryo. To cause fetal growth retardation, the radiation dose must be higher than 25 to 40 rads. As for fetal mental retardation and severe cerebellar disease, the most vulnerable time to radiation damage usually occurs between 8 and 15 weeks of fetal development, followed by after 16 weeks of pregnancy.
Generally during pregnancy, if an abdominal X-ray is taken, the radiation dose is about 122-245 Mrad, which is equivalent to a dose of 0.122-0.245 Mrad. The dose of chest It\’s even more trivial. It is still far from the fetal safe radiation dose threshold of 5,000 megarads. The doses of fetal exposure in various X-ray examinations are shown in Tables 1 and 2.
So unless you\’re undergoing radiation therapy, such as high-dose radiation therapy for cancer, you don\’t need to worry too much. In addition, for nuclear medicine scans during pregnancy, such as bone scans, liver and gallbladder scans, heart and lung scans, brain scans, etc., the radiation dose is within the safe range.
Generally speaking, in radiological nuclear medicine examinations, embryos less than 12 weeks old in the first trimester receive a higher dose in the uterus than those in the second trimester. The only exception is radioactive iodine thyroid scan. After 11 weeks of pregnancy, the fetal thyroid gland receives radioactive iodine. The radiation dose is very high and can cause fetal thyroid damage. If the pregnant woman has medical reasons for needingA computed tomography scan is performed to examine various organs throughout the body, and the radiation dose is within the allowable range of the safe radiation dose threshold. The intrauterine exposure doses of the fetus are shown in Table 3.
Avoid X-rays after ovulation
Even so, as long as a woman is not using birth control, it is best to avoid X-rays after ovulation and, if X-rays are needed, protect the abdomen with a lead plate. There is a famous \”ten-day rule\”, which means that unless it is an emergency, women should choose to take X-rays within ten days after menstruation begins, so that they don\’t have to worry about what to do when menstruation comes. They are pregnant.
There are reports that iodinated contrast media may cause hypothyroidism in some newborns. If a pregnant woman undergoes angiography or computed tomography using iodine-containing contrast media, the newborn is best served with thyroid function screening. As for the safety of fetal MRI examination, so far, there is no literature report that MRI examination will endanger the safety of the fetus and its sequelae.
Avoid MRI in the first trimester of pregnancy
In fact, MRI can be safely performed at any stage of pregnancy if there is a valid medical reason. However, according to the UK\’s National Radiological Protection Society, it is best to avoid MRI scans in the first trimester, as early pregnancy is a critical time for fetal organ development. Additionally, the rate of early-trimester miscarriage is also high (15%), and MRI scans can easily be the culprit.
As for whether the fast resonant electromagnetic current noise generated by MRI scanners will affect the hearing of fetuses in the womb, two reports in the UK showed that fetuses will not suffer hearing damage. It is necessary to use contrast media. MRI contrast agents typically act by modifying the magnetic field effects of nearby hydrogen nuclei rather than by radiopaque drug classification.
It is understandable that some people are concerned about the safety of contrast media and advise against its use. In fact, this contrast agent is commonly used in radiological examinations of newborns and children. In accordance with the recommendations of the American College of Radiology, pregnant women and fetuses are advised to undergo MRI after an in-depth and detailed consultation. The benefits and potential risks of MRI can be leveraged. The European Society of Genitourinary Radiology communication guidelines state that contrast media can be used when pregnant women require MRI for medical reasons. Contrast media should be used in the lowest possible concentration and the required dosage is not recommended in pregnant women with poor renal function as it may lead to nephrogenic systemic fibrosis. MRI is not recommended if you have an allergic reaction to contrast media, are claustrophobic, have a pacemaker, internal metal implants, or surgical metal clips.
Precautions for pregnant women undergoing radiological examinations
The American College of Obstetricians and Gynecologists makes the following recommendations for diagnostic radiography in pregnant women:
Women are accidentally exposed to radiation during pregnancy. We should conduct detailed consultations to reassure them. Any diagnostic radiological examination will not cause radiation damage to the fetus, especially if the radiological examination is smaller than5 rad, that is 5000 mg. Less than safe doses of radiation.
Pregnant women should not refuse necessary diagnostic radiology tests because of concerns about harm to the fetus. Of course, we recommend that if there are other examination methods, B-ultrasound examination or MRI examination without radiation damage can be given priority.
B-ultrasound and MRI showed no suspicion of fetal harm.
When pregnant women undergo diagnostic radiological examinations, they should consult a radiation protection physician about the radiation dose.
Pregnant women should not receive radioisotope iodine treatment.
If there is a need for diagnosis, radiological diagnostic examination requires the use of contrast media, which can be used when the benefits outweigh the risks.
, unlikely to cause potential fetal harm.