National Toxicology Program

Overview

X-rays are a type of penetrating radiation that, depending on the dose, can reduce cell division, damage genetic material, and harm unborn children. Cells that divide quickly are very sensitive to x-ray exposure. Unborn children are particularly sensitive to x-rays because their cells are rapidly dividing and developing into different types of tissue. Exposure of pregnant women to sufficient doses of x-rays could possibly result in birth defects or illnesses such as leukemia later in life. With most x-ray procedures, relatively low levels of radiation are produced. However, a doctor may decide to postpone or modify abdominal or lower back x-rays in a pregnant woman unless absolutely necessary. Women who receive x-rays before realizing they are pregnant should speak to their doctors. Some pregnant women may be exposed to x-rays in the workplace; therefore, the federal government has established limits to protect unborn children from radiation exposure in work settings.

Description of X-rays

X-rays are a type of penetrating radiation (NRC Glossary, 2000). Exposure to x-rays is measured in units of radiation absorbed dose (rad), the amount of radiation absorbed per unit mass of material. Rads are often converted to units of rem by multiplication with quality factors to account for biological damage produced by different forms of radiation. The quality factor for x-rays is 1, so rads and rems are equivalent (NRC 10 CFR 20.1004).

Depending on the dose, exposure to x-rays can result in diminished cell division, damage to genetic material, and damage to unborn children (NRC, 2002, How Does Radiation Affect the Public; FDA CDRH 2001). Rapidly developing cells are very sensitive to x-ray exposure (FDA CDRH 2001). It is important to note that x-rays affect only those body tissues which come into direct contact with the beam. The FDA (FDA CDRH 2001) notes that, "During most x-ray examinations – like those of the arms, legs, head, teeth, or chest – your reproductive organs are not exposed to the direct x-ray beam. So these kinds of procedures, when properly done, do not involve any risk to the unborn child. However, x-rays of the mother’s lower torso – abdomen, stomach, pelvis, lower back, or kidneys – may expose the unborn child to the direct x-ray beam. They are of more concern."

X-rays and pregnancy

Depending on the dose, x-rays could potentially harm an unborn child. The FDA (FDA CDRH 2001) stated that, "There is scientific disagreement about whether the small amounts of radiation used in diagnostic radiology can actually harm the unborn child, but it is known that the unborn child is very sensitive to the effects of things like radiation, certain drugs, excess alcohol, and infection. This is true, in part, because the cells are rapidly dividing and growing into specialized cells and tissues. If radiation or other agents were to cause changes in these cells, there could be a slightly increased chance of birth defects or certain illnesses, such as leukemia, later in life."

Women who have been x-rayed before realizing they are pregnant should discuss this with their doctors. All women who are or may be pregnant should inform their doctors before being x-rayed. Informing doctors about a possible pregnancy allows them to weigh the risks and benefits. The FDA (FDA CDRH 2001) states that, "…the doctor may decide that it would be best to cancel the x-ray examination, to postpone it, or to modify it to reduce the amount of radiation. Or, depending on your medical needs, and realizing that the risk is very small, the doctor may feel that it is best to proceed with the x-ray as planned. In any case, you should feel free to discuss the decision with your doctor."

Occupational X-ray exposure

Federal laws have been established to protect the unborn children of women exposed to radiation in the workplace. In the workplace, the dose of radiation to an unborn child throughout the entire pregnancy cannot exceed 0.5 rem. For x-rays, rem and rad are equivalent and the limit of exposure for unborn children is therefore 0.5 rads (NRC 10 CFR 20.1208).