Common radiological examinations include X-rays, tomography (CT), magnetic resonance imaging (MRI), and ultrasound, of which X-rays and CT are radioactive. The most sensitive period for radiation exposure is the 8th-15th weeks of pregnancy. If a pregnant woman is exposed to ultra-high doses of radiation during this period (20 RAD or more), the risk of fetal malformation or mental retardation increases significantly, and the higher the dose, the greater the chance. However, if the exposure to radiation during this period does not exceed 5 RADs or more, it will not affect the fetus. And there is no scientific proof that radiation causes malformations before the eighth week of pregnancy and after the 25th week!
Below is a table of radiation doses for common radiology examinations.
1 rad = 1000 mrad (1 rad = 1000 howrad)
Radiological examinations
Radiation doses to which the fetus is exposed
Chest X-ray
0.02C0.07 mrad
Abdominal radiograph
100 mrad
Venous pyelography
>=1 rad
Hip radiographs
200 mrad
Mammogram
7C20 mrad
Barium angiography
2C4 rad
CT of head or chest
<1 rad
CT of abdomen or lumbar spine
3.5 rad
CT of pelvis
250 mrad
As you can see from this, it is not easy to reach 5 rad. If you take a chest x-ray at 0.1 mrad, it takes 50,000 chest x-rays to have a possible effect on the fetus. CT is a much higher radiation dose, but even an abdominal CT will not exceed the 5 rad threshold.
To summarize, the current recommendations are as follows.
1. Women should be informed that any single radiology examination done during pregnancy will not have an effect on the fetus. More specifically the radiation dose exposed does not exceed 5 rads or more is not likely to increase the chance of fetal malformation or miscarriage.
2. Pregnant women should not be prevented from having the necessary X-ray examinations because of concerns about the possible effects of radiation. However, if appropriate during pregnancy, consider using a non-radiation test such as ultrasound or MRI instead of CT or X-rays if possible.
3, MRI and ultrasound have no effect on the health of the fetus.
4. If a pregnant woman needs to undergo several or more tests with radiation, she may consider having a radiologist consult to help calculate the radiation dose to which the fetus may be exposed after the test.
5.For some hyperthyroidism patients, radioactive iodine isotopes are not allowed to be used during pregnancy.
It is unlikely that an intravenous contrast agent for enhanced CT or MRI during pregnancy will have any effect on the fetus, however, contrast agents should only be used when the health benefits to the mother are assessed to outweigh the risks.
We hope that the above information will be helpful to some confused mothers-to-be.