Administered radionuclides in pregnancy

Radiopharmaceuticals are occasionally administered to pregnant patients eit her out of clinical necessity or by accident. In recognition of the latter, the Society of Nuclear Medicine recommends pregnancy testing before any pr ocedure that will expose the fetus to >50 mGy. When pregnancy is known, the dose of radionuclide to be employed is kept as low as possible without sac rificing radiographic information. The commonly administered radiopharmaceu ticals used for lung, gallbladder, kidney, bone, and bleeding scans are lab eled with technetium-99m: all deliver whole fetal doses of <5 mGy. These do ses are lower than those known to produce deterministic effects, and are li kely to be very conservative, since radionuclide exposure delivers protract ed irradiation exposures to the embryo and fetus. The actual deterministic risks will decrease with the magnitude of the protraction as compared with the acute effects of irradiating the embryo and fetus. The probability of l ate effects is considered sufficiently low not to contraindicate the use of these radiopharmaceuticals when medically required or to raise undue conce rn when they are accidentally administered. (C) 1999 Wiley-Liss, Inc.