Antepartum dental radiography and infant low birth weight.

CONTEXT Both high- and low-dose radiation exposures in women have been associated with low-birth-weight offspring. It is unclear if radiation affects the hypothalamus-pituitary-thyroid axis and thereby indirectly birth weight, or if the radiation directly affects the reproductive organs. OBJECTIVE To investigate whether antepartum dental radiography is associated with low-birth-weight offspring. DESIGN A population-based case-control study. PARTICIPANTS AND SETTING Enrollees of a dental insurance plan with live singleton births in Washington State between January 1993 and December 2000. Cases were 1117 women with low-birth-weight infants (<2500 g), of whom 336 were term low-birth-weight infants (1501-2499 g and gestation > or =37 weeks). Four control pregnancies resulting in normal-birth-weight infants (> or =2500 g) were randomly selected for each case (n = 4468). MAIN OUTCOME MEASURES Odds of low birth weight and term low birth weight by dental radiographic dose during gestation. RESULTS An exposure higher than 0.4 milligray (mGy) during gestation occurred in 21 (1.9%) mothers of low-birth-weight infants and, when compared with women who had no known dental radiography, was associated with an adjusted odds ratio (OR) for a low-birth-weight infant of 2.27 (95% confidence interval [CI], 1.11-4.66, P =.03). Exposure higher than 0.4 mGy occurred in 10 (3%) term low-birth-weight pregnancies and was associated with an adjusted OR for a term low-birth-weight infant of 3.61 (95% CI, 1.46-8.92, P =.005). CONCLUSION Dental radiography during pregnancy is associated with low birth weight, specifically with term low birth weight.