How does radiation exposure affect unborn babies?

Do you know how radiation exposure could affect your unborn baby?

Not all types of radiation are created equal. This means that depending on its origin, radiation can be fairly benign or incredibly malignant. Many natural sources exist, such as sunlight, rocks, soil and food. There are also plenty of human-derived emitters, such as airport security screeners, medical procedures like X-rays, cell phones and nuclear weapons.

"We're all exposed to radiation on a daily basis," explains Kelly Classic, a radiation physicist at the Mayo Clinic, and public outreach coordinator for the Health Physics Society -- noting that small amounts of radiation can be found in fertilizers, some soils, building materials and even bananas, because of their naturally occurring potassium. "It's something that we live with every day and so rarely question it."

All forms of radiation, whether from sunlight or a computer, operate on the electromagnetic scale -- each with its own, varying frequency, wavelength and energy emitted. Depending on the amount of energy they have, the wavelengths can travel certain distances and penetrate certain objects. Longer wavelengths, like those used in cell phones, garage door transmitters and AM/FM radios, have lower energies and lack the ability to cause changes to atoms. People are exposed to low-intensity radiation throughout each day, giving it the name background radiation exposure. Most people in the U.S. are exposed to about 3 millisieverts (mSv) worth of natural radiation each year, an amount that is presumed harmless [source: Classic]. The mSv is a measure of the amount of radiation absorbed by the human body.

It's when one adds higher intensity radiation to this everyday exposure that health concerns begin. As wavelengths become shorter, their energy intensity continues to increase until it becomes ionizing, or causes changes to the cellular structure of atoms. Ionizing radiation is the most powerful form of radiation is, and it can be used to produce electricity, treat cancer, take X-rays and sterilize medical instruments. Ionizing radiation is more worrisome, especially when unborn babies come into contact with it, since it can have serious health ramifications.

What would cause a baby to be exposed to radiation?

Today, the most common source of prenatal radiation exposure is medical exams, such as a computerized axial tomography (CT or CAT) scan of the abdomen or pelvis, lower back X-rays, or standard pelvic X-rays. It can also come from the backscatter X-ray at the airport. Less common causes of radiation exposure could include nuclear power plant accidents, detonation of an atomic bomb or nuclear weapons testing.

Unborn babies are more susceptible to the health effects of radiation, especially in the very early weeks immediately following conception, since they are comprised of fewer cells, which are dividing rapidly, and therefore more likely to be disrupted by the effects of radiation. In turn, their development can be greatly impacted. This means that between the second and 18th week of pregnancy, mothers should be particularly cautious about radiation exposure [source: Centers for Disease Control and Prevention]. Since an unborn baby is still developing, radiation levels that may have no impact on the mother can harm them.

The most common effects of in utero radiation exposure are impaired growth, physical deformities like smaller head size, irregular brain performance, or cancers that may develop later in the baby's life [source: Classic]. Of the cancers associated with radiation exposure, leukemia and cancers of the thyroid, lung and breast are the most common [source: WebMD]. However, the womb sometimes serves as a safe house of sorts for the baby. It can shield the baby from the total amount of radiation the mother is being exposed to, limiting the harm caused.

If you're pregnant and are at all concerned about the possibility of being exposed to radiation, consult your doctor immediately. According to the Health Physics Society, common types and levels of radiation exposure include:

  • Natural background radiation for the average American each year = 3 millisievert (mSv)
  • Natural background radiation from living at high-altitudes, such as Denver: 6 mSv/year
  • CT of abdomen or pelvis= 7 to 14 mSv
  • Mammogram = 1 to 2 mSv
  • X-ray of lower back = 0.8 mSv
  • X-ray of chest = .1 to .6 mSv
  • One backscatter X-ray screening for security at an airport= 0.0038 mSv

The risks of radiation exposure can vary based on the gestational stage. Keep reading to learn more.

How can radiation affect a fetus at its various gestational stages?

The risk your unborn baby faces from radiation depends on his or her stage of development.
The risk your unborn baby faces from radiation depends on his or her stage of development.

The time during which a fetus develops inside the mother's womb is vital for healthy growth. Radiation exposure before a baby's birth can increase the likelihood of disease -- such as cancers later in life -- or even end the child's life before it's barely begun. Since unborn babies are especially sensitive to radiation, it's best if an examination that involves radiation exposure can be postponed or replaced with another until after the baby is born [source: Classic].

Even so, the risk depends on the amount of radiation the unborn child is exposed to. The CDC measures the threshold for safe exposure by comparing it to the amount of radiation in 500 chest X-rays or less (.1 to .6 mSv x 500), which is deemed a low-dose. A high dose of radiation is considered to be the amount in 5,000 chest X-rays or higher [source: CDC]. Should an unborn baby be exposed to 500 chest X-rays worth of radiation or less at one time, the only health concern is that their risk of cancer could increase by less than 2 percent than the average rate.

  • The first couple weeks of pregnancy: Radiation exposure causes the greatest concern during the early weeks of pregnancy and can have an all-or-nothing effect on the embryo during the first eight days following conception [source: Health Physics Society]. During this time, the embryo is comprised of only a few cells, so a large dose of radiation dose could trigger a miscarriage or have no effect on the embryo at all.
  • Between 2 and 18 weeks of pregnancy: Around the eighth week of pregnancy, an embryo becomes a fetus. Around this time, there can be harmful health impacts to an unborn baby should it be exposed to radiation levels above the amount in 500 chest x-rays. The possibilities include brain damage, and a wide range of birth defects.
  • Between 18 weeks and full-term pregnancy: At this point in pregnancy, the fetus has outgrown its most fragile development stages. A mother-to-be can breathe a sigh of relief now that her unborn child is no longer any more susceptible to radiation than a newborn. Of course this doesn't mean all is free and clear, just a bit more protected.
  • 26 weeks and beyond: A fetus has now developed enough to resist many of the birth defects linked to pregnancy and radiation exposure since it is fully developed, although it will continue growing longer and heavier.

For more detailed information about how radiation levels can affect a fetus at different stages of development, see the CDC's"Radiation and Pregnancy" fact sheet.

Are there examples of fetal radiation damage occurring in history?

The two most frequently cited nuclear contamination events are the bombing of Hiroshima and Nagasaki, and the Chernobyl meltdown. There's also the recent disaster at the Fukushima Daiichi nuclear power plant in Japan, although impacts from this meltdown may not be understood for a long while. So let's look back at history.

In 1945, the U.S. dropped two atomic bombs on the cities of Hiroshima and Nagasaki in hopes of ending World War II. The plan worked, although many of the health impacts came as an unfortunate lesson that hindsight is 20/20. Since then, researchers have tracked the survivors and discovered that babies exposed to the bomb's radiation while still in utero were found to have lower IQs, higher rates of mental disability, and impaired physical growth and development. [source: Radiation Effects Research Foundation].

Another infamous example is that of the Chernobyl nuclear power plant disaster in the Ukraine. In 1986, the plant's reactor No. 4 exploded, disseminating radiation over Belarus, Russia and areas in northern Europe. Thirty-one people died in the first few weeks following the disaster from radiation sickness [sources: Mayo Clinic; World Nuclear Association]. Research has also shown that children from the areas surrounding Chernobyl have an unusually high rate of thyroid cancer, stunted growth, unhealthy teeth and gums, immune system disorders and a much higher rate of thyroid cancer [source: Chernobyl Children's Project].

The thyroid is the only organ in the human body that uses iodine, so if we take in radioactive iodine, the body shuttles it straight to the thyroid where cellular mutations can then occur, possibly causing cancer [source: Classic]. After the Chernobyl explosion, radioactive iodine blanketed the cow fields and, through digestion, it became incorporated into cows' milk and was passed on to the children who drank it [source: World Health Organization]. The effects of Hiroshima, Nagasaki and Chernobyl are still being felt today.

Ask your physician if you have a specific concern about radiation exposure and your unborn baby. For more information on the topic, visit the links and articles on the next page.

Related Articles


  • Centers for Disease Control and Prevention. "Radiation and Pregnancy: A Fact Sheet for the Public." March 29, 2011. (July 15, 2011).
  • Chernobyl Children's Project. "The effects of the Accident on Human Health." 2011. (June 20, 2011)
  • Classic, Kelly. Public Outreach Coordinator for the Health Physics Society. Personal interview. July 15, 2011.
  • The Daily Beast. "How Will Radiation Affect Unborn Babies in Japan?" March 15, 2011. (July 14, 2011).
  • Health Physics Society. "Fukushima News." July 8, 2011. (July 15, 2011).
  • Mayo Clinic. "Radiation Sickness." March 17, 2011. (July 14, 2011).
  • Radiation Answers. "Types of Radiation." 2007. (July 18, 2011)
  • Radiation Effects Research Foundation. "Radiation Health Effects on Survivors." 2002. (July 18, 2011)
  • WebMD. "Nuclear Meltdown in Japan: What's the Risk of Radiation?" March 18, 2011. (July 18, 2011).
  • World Health Organization. "Health effects of the Chernobyl accident: an overview." April 2006. (July 15, 2011).
  • World Nuclear Association. "Chernobyl Accident 1986." 2011. (July 20, 2011).