Guide to the Safe use of Radionuclides at the University of Wisconsin - Milwaukee
Section 24: Prenatal Radiation Exposure
Since 1906, it has been known that plant and animal cells are most sensitive to radiation damage when they divide rapidly and when they are relatively unspecialized in their function. Thus, the human embryo or fetus is more susceptible to radiation injury than is an adult. It is also known that in the first 8-15 weeks of pregnancy the fetus is most sensitive to radiation. This stage includes the time period in which a woman might be unaware of her pregnancy.
When a woman is pregnant, exposure of her abdomen to sufficiently penetrating radiation from external sources or from internally deposited sources also exposes her unborn baby. As stated above, the unborn is most sensitive to radiation during the first 3 months after conception, the time when a woman may not be aware she is pregnant. Therefore, all Authorized Users and Radiation Workers must read and understand NRC Regulatory Guide 8.13, "Instruction Concerning Prenatal Radiation Exposure" (Appendix T) prior to working in a radionuclide laboratory or facility.
24.1 Fetal Protection Policy
Title VII of the Civil Rights Act of 1964, as amended by the Pregnancy Discrimination Act, forbids sex-specific fetal-protection policies. In the 1991 Supreme Court decision involving Johnson Controls the court ruled "It is inappropriate...for individual employers to decide whether a woman's reproductive role is more important to herself and her family than her economic role. Congress has left this choice to the woman as hers to make." The preamble to 10 CFR Part 20 states "It is the fundamental responsibility of the pregnant worker to decide when or whether she will formally declare her condition to her employer...having a woman formally declare her pregnancy to her employer derives from legal, not health protection, considerations."
For those reasons, "special" prenatal exposure limits are applied only to the "declared pregnant woman." It is each woman's choice to formally declare her pregnancy to the University.
24.2 Pregnancy Declaration
Women choosing to declare their pregnancy should contact the Radiation Safety Program. Formal declaration must be made in writing and should include the estimated month of conception. Please note that it is the policy of this office to regard this information as personal and private.
24.3 Exposure Limits for the Embryo or Fetus
The NRC requires that the dose to an embryo or fetus during the entire pregnancy from occupational exposure to radiation to the "declared pregnant woman" (see Sections 24.1 and 24.2) must not exceed 0.5 rem. The regulations also require that substantial variations in the monthly rate of exposure be avoided. Thus, the dose should be incurred at a fairly uniform rate over the entire gestation period and not be incurred in a few large doses. The NRC does permit an additional 0.05 rem of exposure if the pregnant worker has >0.45 rem at the time her pregnancy is declared.
24.4 Monitoring
The dose equivalent to the embryo or fetus should be determined based on the monitoring of the declared pregnant woman. External monitoring should be performed to determine the external dose of the embryo or fetus if the declared pregnant woman is likely to receive a deep-dose equivalent in excess of 50 mRem for the entire gestation period. Monitoring of the intake of radionuclides by the declared pregnant woman should be performed for determining the internal dose to the embryo or fetus if the intake is likely to exceed 1% of the annual limit of intake (ALI) during the gestation period.
Updated March 4, 2008 by SAK