What are the risks to the fetus associated with diagnostic radiation exposure during pregnancy?

Clinicians have been concerned about x-ray exposure during pregnancy since the 1950s. Much of this concern was based on the Oxford Survey of Childhood Leukemia, as well as other early case-control studies. These studies reported an approximate 40% increase in the risk of childhood leukemia among offspring of women who received diagnostic x-rays in pregnancy. However, by modern standards, these studies are of poor quality as they are limited by reliance on maternal recall of prenatal x-ray exposure, lack of consideration for multiple confounding factors, lack of blinding in determination of exposure and outcome status, limitations in selection of both cases and controls, and other significant methodological flaws. Modern, well-designed studies have failed to replicate the association between in utero radiation and childhood malignancies found in the early studies. We found 1 good-quality and 5 fair-quality case-control studies examining the association between in utero x-ray exposure and childhood leukemia, as well as 6 fair-quality case-control studies examining the association with other childhood malignancies. These studies found no significant association between in utero exposure to any x-ray in general, or to abdominal or pelvic x-rays and development of subsequent childhood leukemia, central nervous system tumors or other malignancies (TABLE). No meta-analyses, randomized controlled trials, cohort studies or good- or fair-quality case-control studies were found examining in utero x-rays and decreased head circumference, congenital malformations, spontaneous abortion, low birth weight, or developmental problems. One recent, fair-quality case-control study found an association between prenatal dental x-rays and low birth weight (odds ratio [OR]=1.8 [95% confidence interval, 1.09-1.36]) for radiation exposures above 0.4 Gy. However, this study has been criticized for several reasons, including lack of biological plausibility and failure to control for dental disease. There does not appear to be an increased risk of adverse pregnancy outcomes with prenatal endoscopic retrograde cholangiopancreaticogram (ERCP), though this conclusion is based on 2 incomplete case series reports with no follow-up of the infants after delivery. No good- or fair-quality studies were found examining the association between other diagnostic radiation exposures (CT scan, mammography, positron emission tomography scan, dual-energy x-ray absorptiometry [DEXA]) with adverse pregnancy outcomes.