Maternal exposure to ionizing radiation and birth defects
Abstract
This doctoral dissertation research covered two main objectives focused on maternal exposure to ionizing radiation (IR) and birth defects using the data from the National Birth Defects Prevention Study (NBDPS), an ongoing, large population-based study of birth defects. The first objective was to assess the association between suspected maternal occupational exposure to IR and birth defects. Exposure assessment was based on maternal answers on the NBDPS questionnaire that asks mothers about their occupations during the periconceptional period. Logistic regression was used to assess odds ratios (ORs) for the association between maternal occupations with suspected exposure to IR and 39 birth defects. No association was observed between maternal occupations with suspected exposure to IR and all birth defects in aggregate compared to other occupations (odds ratio [OR] = 0.9; 95% confidence interval [CI] = 0.7 - 1.1). There were 4 significant associations between maternal occupations with suspected exposure to IR and isolated hydrocephaly (OR= 2.3; 95% CI= 1.2 - 4.4), isolated anotia/microtia (OR= 2.0; 95% CI= 1.0 - 4.0), isolated colonic atresia (OR = 7.5; 95% CI = 2.5 - 22.3), and isolated omphalocele (OR = 2.3; 95% CI = 1.2 - 4.7). In addition, a non-significant association was observed between suspected maternal exposure to IR from fluoroscopy and birth defects in aggregate (OR=2.1; 95% CI=0.9 – 4.6). Despite a finding of increased risk for 4 of 39 isolated defects, it is possible that these associations were due to other occupational exposures that are correlated with occupational exposure to IR and we also cannot rule out the possibility that some of our findings may be due to chance. The second objective was to investigate the association between maternal exposure to radiologic exams that deliver moderate to high levels (>1.0 mGy) of IR to the pelvis and birth defects. Maternal exposure to radiologic exams that deliver >1.0 mGy to the pelvis were determined based on the mother's report of type of radiologic exams, organ or body part scanned and the month during which the exam occurred. Logistic regression was used to assess ORs for the association between maternal exposure to radiologic exams that deliver >1.0 mGy to the pelvis and 23 specific categories of birth defects and a final category of all NBDPS birth effects in aggregate. No association was observed between maternal exposure to radiologic exams that deliver >1.0 mGy to the pelvis from three months before conception to conception and any of these birth defect categories. A significant association was observed between maternal exposure to radiologic exams that deliver >1.0 mGy to the pelvis during the first trimester and isolated d-transposition of the great arteries (OR= 3.8; 95% CI= 1.4 – 10.3). However, there is a possibility that recall bias may be present because exposure measurements were based on mothers' recall of radiologic exams. Also, there is a possibility that some of results may be due to chance. Overall, this doctoral dissertation research found no significant association between maternal occupations with suspected exposure to IR and all birth defects in aggregated, and no significant association between maternal exposure to radiologic exams that deliver >1.0 mGy of IR to the pelvis and all birth defects in aggregate. Although, the association between exposure to IR and the frequency of several phenotypes of birth defects was increased these results should be interpreted cautiously. The results of this study are likely to be useful for generating hypotheses for further studies of exposure to IR.
Subject Area
Occupational health|Womens studies|Environmental Health|Public health|Nuclear physics
Recommended Citation
Lim, Hyeyeun, "Maternal exposure to ionizing radiation and birth defects" (2014). Texas Medical Center Dissertations (via ProQuest). AAI3665021.
https://digitalcommons.library.tmc.edu/dissertations/AAI3665021