Radiation Risks for Pregnant Women, Unborn Children: Questions and Answers
Radiation Risks in Pregnancy, for Babies
Haruyoshi Yamaguchi/Bloomberg
Mothers receive bottles of water at a distribution office in the Adachi ward of Tokyo.
Mothers receive bottles of water at a distribution office in the Adachi ward of Tokyo. Photographer: Haruyoshi Yamaguchi/Bloomberg
Radiation from Tokyo Electric Power Co.’s damaged nuclear power plant in northeastern Japan has contaminated food, water and the environment.
Radioactive Iodine-131 was detected at 210 becquerel per kilogram at a water purification plant in Tokyo, exceeding a limit of 100 Bq/kg for infants, the city’s water department said on March 23. Reported levels of radioactivity have since declined.
Here are answers to some frequently asked questions about the effects of radiation on pregnant women and their unborn babies. The information was compiled from the websites of the World Nuclear Association, the U.S. Food and Drug Administration, the Centers for Disease Control and Prevention and the International Atomic Energy Agency.
Q: Can radiation harm a fetus? A: Potentially, yes. Children and unborn babies are more sensitive to radiation than adults because their cells are dividing frequently as they grow. Radiation can disrupt that process, increasing the risk of birth defects, leukemia or mental retardation. Following the Chernobyl accident there has been no increase in congenital abnormalities or adverse pregnancy outcomes, according to the World Nuclear Association.
When a fetus is exposed to radiation equivalent to at least 500 chest X-rays during the more sensitive stages of development, the health consequences can be severe, especially to the brain. Fetuses exposed to the atomic bombs dropped on Hiroshima and Nagasaki, Japan, during the 8- to 15-week stage of pregnancy were found to have a high rate of brain damage that resulted in lower IQs and even severe mental retardation. They also suffered stunted growth (as much as 4 percent shorter than average) and an increased risk of other birth defects.
Q: Is there a safe or unsafe level of radiation exposure during pregnancy? A: Unborn babies, particularly from the second to 15th week of pregnancy, are especially sensitive to the cancer-causing effects of radiation. A dose of 100 millisieverts or more may result in the death of the fetus in the earliest stages of pregnancy.
The level of increased risks depend on the amount of radiation to which the fetus was exposed and the duration of exposure. For example, if the radiation dose to the unborn baby was roughly equivalent to 500 chest X-rays at one time, the increase in lifetime cancer risk would be less than 2 percentage points greater than the normal lifetime cancer risk of 40 percent to 50 percent.
Q: At what period of development is radiation of biggest concern to a fetus? A: The embryo is made up of only a few cells during the first two weeks of pregnancy. Damage to one cell can cause the death of the embryo before the mother even knows that she is pregnant. Of the babies that survive, however, few will have birth defects related to the exposure, regardless of how much radiation they were exposed to.
In the 16- to 25-week stage of pregnancy, health consequences similar to those seen in the 8- to 15-week stage could occur, but only when the doses equate to more than 5,000 chest X-rays at one time. At this dose level, the mother could be showing signs of acute radiation syndrome, which is sometimes known as radiation sickness.
At the 26th week of pregnancy, the fetus is fully developed, though not fully grown. Unborn babies exposed to radiation in the womb during this stage of pregnancy are no more sensitive to the effects of radiation than are newborns. This means that birth defects are not likely to occur, and only a slight increase in the risk of having cancer later in life is expected.
Q: Does a fetus receive the same amount of radiation as the mother? A: Since the fetus is shielded by the mother’s abdomen, it is protected in the womb from radioactive sources outside the mother’s body. Consequently, the radiation dose to the fetus is lower than the dose to the mother for most radiation exposure events.
To contact the reporters on this story: Simeon Bennett in Singapore at sbennett9@bloomberg.net
To contact the editor responsible for this story: Jason Gale at j.gale@bloomberg.net
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