Radiation Exposure, Pregnancy, and Reproductive Risks
The following information pertains to radiation exposures of women who are pregnant and have questions about the risk of birth defects and miscarriage. It is also for men and women who are concerned about radiation exposures they have had that might impact the development of their sperm or their eggs (ova) and their risk of passing on genetic diseases because of the radiation exposure.
Basic Concepts
The next paragraphs contain basic concepts as an introduction to help understand the more specific information provided later. It must be remembered that every healthy woman without a personal or a family history of reproductive or developmental problems begins her pregnancy with a 3 percent risk for major birth defects and a 15 percent (~ 1 in 7) risk for miscarriage. These are the normal background risks for all healthy pregnant women.
Ionizing radiation is the kind of electromagnetic radiation produced by machines used in radiology or radiation oncology and radioactive isotopes (radionuclides). The unborn child might be exposed to radiation during diagnostic or therapeutic procedures when a pregnant woman has x rays, fluoroscopy, or radiation therapy, or is administered liquid radioactive materials. To determine the risks of a radiation exposure for the unborn child, it is best to request from your physician, a consultation from a health physicist who works at or consults for the organization where the procedures are to be or were performed. In many instances, especially cases of diagnostic exams, an evaluation of the radiation exposure is not necessary because the radiological exam will not or did not expose the developing unborn child.
Typical diagnostic procedures (chest x ray, foot x ray, abdominal x ray, lung CT scan, etc.) expose the unborn child to well less than 5 rad or 50 mGy. This level of radiation exposure will not increase risks of birth defects or miscarriage. However, some therapeutic and interventional radiological procedures may result in higher exposures (this might be radiation therapy of the pelvis for a cancer using a linear accelerator). According to published information, the reported dose of radiation necessary to result in an increased incidence of birth defects or miscarriage is above 10-20 rad or 100-200 mSv. Generally, for the unborn child to receive this high a radiation dose from a medical procedure, the procedure will need to be some form of high dose radiation therapy in the abdominal area for disease treatment.
Stages of Pregnancy
An important consideration is the stage of pregnancy in which the radiation exposure occurred:
- Weeks 1-2
In the first two weeks of pregnancy or the second two weeks from the last menstrual period, the unborn child is resistant to the harmful effects of x rays. Miscarriage is not likely to occur if the radiation dose is less than 50 rad (500 mSv). - Weeks 3-8
From the third to the eighth week of pregnancy, the unborn child is in the period of early development but is not noticeably affected with birth defects, pregnancy loss, or growth retardation unless the exposure is above 50 rad (500 mSv). - Weeks 8-15
From the eighth to the fifteenth week of pregnancy, the unborn child is sensitive to the effects of radiation on the central nervous system. Growth retardation and mental retardation may occur at doses above 5 rad (50 mSv). The threshold for an observable reduction in IQ has been estimated to be higher than 30 rad (300 mSv). General diagnostic studies do not reach these levels and, therefore, these effects are rarely of concern for patients. - Weeks 20 and On
Beyond the twentieth week of pregnancy when the unborn child is completely developed, it has become more resistant to the developmental effects of radiation. The most important thing is that practically none of the diagnostic radiological procedures will affect an unborn child at this late stage of pregnancy and certainly there is no risk for birth defects or miscarriage from the range of exposures that occur from diagnostic studies.
The reproductive risk of nonionizing radiation is minimal, if it even exists. This statement is the result of two national committee studies evaluating nonionizing radiation sources and pregnancy. Nonionizing sources that were in the studies include the electromagnetic fields emitted from computers, microwave communication systems, microwave ovens, power lines, cellular phones, household appliances, heating pads and warming blankets, airport screening devices for metal objects, and diagnostic levels of ultrasound.
Radiation Exposure to the Unborn Child or Ovaries from Diagnostic X-Ray Studies
The most important issue is actual radiation dose received by the unborn child. When a diagnostic x-ray study is taken of the head, teeth, chest, arms, neck, or legs at a qualified facility, there is little or no radiation exposure to the unborn child or ovaries. Scattered radiation that might reach the unborn child, if any, would be extremely small and would not represent an increased risk for birth defects or miscarriage. From other diagnostic x-ray studies, including computerized tomography (CT or CAT) scans and fluoroscopy of the area outside the lower abdomen, the developing unborn child would not receive a dose that would result in any measurable increased risk.
Diagnostic x-ray studies that may involve direct radiation exposure of the developing unborn child include (1) x rays of the back (lumbar spine) for evaluating a lower-back pain or a nerve-route pain, (2) an intravenous pyelogram (IVP) to examine kidney function, (3) an upper GI series for evaluation of gastrointestinal symptoms, (4) a lower GI series (barium enema) to examine the structure and function of the large intestine, (5) x-ray studies of bladder function, (6) x-ray studies of the gallbladder and gallbladder function, (7) x-ray studies of the structure and function of the uterus and tubes with the procedure known as a hysterosalpingogram (HSP), (8) x-ray studies of the pelvis and hips for evaluating hip pain, (9) CT scans of the abdomen or pelvis, and (10) standard abdominal x rays.
These studies may expose the unborn child to radiation. However, the x-ray beam in the above-mentioned procedures may or may not be directed toward the unborn child. In some cases, the unborn child may not be exposed at all and, in others, the unborn child may be exposed for only a portion of the study. If a pregnant woman is considering or has had any of these procedures and has questions regarding radiation dose, the first step is to have someone in the radiology department or a health physicist at the institution where the procedure(s) is to be or was performed estimate the actual radiation dose that may be or was received by the unborn child.
There are two important facts to consider when an evaluation is performed. First, the exposure in the vast majority of instances will be low and will not represent a reproductive risk for the unborn child for birth defects or miscarriage. Second, regardless of the dose received from these procedures, each woman must realize that when she begins a pregnancy she has a reproductive risk (referred to as background risks) of 3 percent for major birth defects and 15 percent for miscarriage. These risks change depending on the family history of the mother and her own reproductive history.
Radiation Exposure to the Unborn Child from Diagnostic Nuclear Medicine
Pregnant women may be administered radioactive materials for the treatment of various medical conditions while they are pregnant. Some of these radioactive materials may be administered before the patient knows that she is pregnant. Nearly all of the types of radioactivity that will be administered for a nuclear medicine exam will also expose the unborn child to radiation.
In most cases, even though the unborn child will be exposed, it is not enough radiation dose to cause harmful effects. In a few cases, however, the type and amount of radioactivity and the age of the unborn child combine such that there might be harmful effects. The most frequent case of this occurring is when if the woman has thyroid problems and is given radioactive iodine after the ninth week of pregnancy. Luckily, though, by the ninth week, most women know they are pregnant and can discuss with their physician the need for the radioactive iodine exam, whether it can wait seven more months, and possible harmful effects for the unborn child.
Radiation Exposure to the Unborn Child from Therapy Procedures that Do or Could Involve Exposure to the Abdomen
One form of radiation therapy for cancer and other diseases is the administration (oral or by injection) of radioactive materials to treat various diseases. The most common of these is oral administration of radioactive iodine, which is used to treat hyperthyroidism or cancer of the thyroid. In another form of therapy, radioactive seeds can be placed into various organs and tissues to treat cancer. And finally, radiation emitted from large machines (linear accelerators or teletherapy units) can be used to treat cancer and other diseases. Before any of these procedures, physicians will take a pregnancy into consideration, so in nearly all instances, these uses of radiation will not occur when a woman is pregnant. Physicians who believe that delaying the procedure until the child is born would be a significant risk to the mother may decide to proceed and will share with her the possible risks of the radiation exposure to the unborn child.
Occasionally, radioactive iodine for the treatment of hyperthyroidism or cancer of the thyroid is administered to a woman who may not yet know she is pregnant. In these instances, it is essential that the exposure to the unborn child be determined before any counseling can be provided. It is recommended that this determination be obtained from the health physicist, a nuclear medicine physician, or a radiation oncologist associated with the institution where the procedure took place.
Since radiation treatment for cancer involves quite high doses of radiation, in the thousands of rad (tens of gray), it is very likely that the unborn child will be affected if radiation therapy is initiated during pregnancy. In this case, if the mother is receiving radiation therapy of the lower abdomen for cancer treatment, the unborn child may not survive. When exposures occur later in gestation, unborn child sensitivity may be less and the unborn child might survive, but there is still concern about radiation effects even though the unborn child might survive.
It is possible that even with radiation therapy to other parts of the body the unborn child might receive an exposure that increases the risk of biological effects. Again, it is essential that the exposure to the unborn child be determined before any counseling can be provided. It is recommended that this determination be obtained from the health physicist, a nuclear medicine physician, or a radiation oncologist associated with the institution where the procedure is to take place or has occurred.
Family Members or Friends Receiving External Beam Radiation Therapy
Radiation therapy does not cause the patient to become radioactive and be a source of radiation exposure to others. Therefore, contact with individuals receiving external radiation therapy does not have to be changed or limited.
Family Members or Friends Administered Radioactive Materials for Diagnosis or Therapy
If family members or friends have been administered radioactive materials for diagnosis or therapy; they will contain some residual radioactivity when they leave the facility. After a diagnostic procedure, they will be allowed to leave immediately unless there are other reasons for which they need to be hospitalized. In these cases, they have been administered a small amount of radioactive materials—only enough to successfully perform the procedure. There are no special concerns about interacting with them.
It might be different, however, if radioactive material was received for a therapy procedure. In some cases, patients might have to stay in the hospital for a few days because they received quite a bit of radioactivity. Even when they are allowed to go home, the amount of radioactivity they still have inside them may be more than they would have with a diagnostic procedure. Depending on when patients are allowed to leave and how much radioactivity was administered, there may or may not be any special precautions. In cases where additional guidelines are needed, patients are given instructions from the healthcare provider regarding extra precautions to be taken. Some of these precautions might include limiting time around children or someone who is pregnant. If you are a family member, you can discuss these precautions directly with the physician. If your friend underwent the procedure, he or she would have received the information and can discuss your concerns with you.
Radiation Effects on the Egg and Sperm
Genetic effects (those that are seen in the children of the exposed person) are possible when the egg or sperm is irradiated; however, this effect has not been demonstrated in humans. The concern of most patients is whether radiation exposure to the egg or sperm will result in birth defects. The risk from radiation exposure to the egg or sperm prior to conception has been studied in two large populations. In one study, thousands of patients who were exposed to radiation in Hiroshima and Nagasaki and had families were studied for the incidence of genetic disease and other reproductive effects. After 50 years of study on this population, there has been no demonstrable increase in genetic disease found. What was learned is that the risk is extremely small and that you need very large populations to demonstrate this risk. In other words, the risk from the radiation is too small to be detected amid the spontaneous incidence of mutations and the hereditary component of mutations that may affect the offspring.
Similarly, the National Cancer Institute has studied men whose testes were exposed during radiation therapy as well men who received chemotherapy with drugs and chemicals. There are now several thousand patients who have survived cancer which occurred in childhood, adolescence, or early adulthood. Families of these individuals also have not demonstrated an increase in birth defects or miscarriage.
It is possible that infertility or sterility may result if the testes receive high exposures of radiation. Because of the theoretical risk, men may be advised to wait for at least two spermatogenesis cycles (about four months) before trying to parent a child.
Radiation Exposure to the Sperm from Radiation Therapy
External beam radiation therapy of the pelvis, hip, femur (upper long bone of the leg), bladder, and prostate cause radiation exposure to the testes. While it is possible to shield the testes for some of these radiation procedures, the radiation dose from scattered radiation could still be quite high. With very high doses to the testes the main complication is temporary or permanent sterility. For those patients who remain fertile after therapy, the reproductive risks are not increased significantly. In other words, the risk of birth defects in the next generation for those men who remain fertile and conceive is quite low.
Studies of the atomic bomb survivors indicate that even in the high-exposure group that there is not an increased incidence of chromosome abnormalities or genetic disease in the next generation. That is also the case for studies from the National Cancer Institute, which indicate that for patients who had cancer and received chemotherapy and radiation, there was no increased incidence in genetic disease or birth defects in the next generation although the patients did have problems with infertility.