Spontaneous Abortions Among U.S. Occupationally Exposed Radiologic Technologists

Introduction Radiologic Technologists exposed to continuous low dose radiation may have an increased risk for spontaneous abortions. Although the federally mandated radiation dose limit to the developing fetus of an occupational worker is 5mSv, well below the documented threshold of 100mSv, some studies have suggested an increased risk for spontaneous abortions in occupationally exposed females. The effects of exposure to low levels of radiation are difficult to discern from the usual occurrence and are limited in the literature because of the large sample size needed to achieve statistical power. This study contains data from 152,439 self-reported pregnancies and possesses the appropriate sample size to assess the risk of spontaneous abortions incident to radiologic technologists who maintain fetal radiation dose levels within federal guidelines. Methods This non-experimental retrospective designed study uses data from the United States Radiologic Technologist Study (USRTS). The USRTS began in 1982 as a joint effort between the American Registry of Radiologic Technologists (ARRT),UniversityofMinnesotaand the National Cancer Institute to study the radiation effects from low-dose occupational exposure. This longitudinal study follows more than 90,000 current and former technologists through periodic surveys and contains a sufficient sample size to overcome statistical power concerns. The provided data included the order and outcome of each self-reported pregnancy as well as the year of each live birth. The data were therefore manipulated to provide a likely gestational interval for both a reported live birth and spontaneous abortion. After calculating the spontaneous abortion rate for the final sample, a binary logistic regression was performed to determine if levels of estimated fetal radiation dose are associated with predicting the odds of a reported spontaneous abortion. A linear regression analysis was then performed to assess the relationship between the calculated odds ratios of a reported spontaneous abortion as a function of estimated fetal radiation dose, specifically to determine the significance of the linear relationship Results The overall spontaneous abortion incidence to the cohort reporting at least one live birth or spontaneous abortion was 14.8%, lower than the reported national incidence of 15-20%. Using up to 1mSv as the reference fetal radiation dose category, the odds ratios of a spontaneous abortion for 1-2mSv, 2-3mSv, 3-4mSv and 4-5mSv were calculated as 1.57, 1.82, 2.11 and 2.15 respectively. This increase in odds was linear with estimated fetal radiation dose as demonstrated by the significant regression equation (F=29.93, p = .01) and an R2 of 0.9089. Conclusions By demonstrating an increased risk at levels of radiation as low as natural background, and further demonstrating the risk increases linearly with radiation dose, the Linear Non-Threshold Theory appears to be the more likely risk model for predicting spontaneous abortions in lieu of the belief that a 100mSv threshold must first be exceeded for a radiation induced spontaneous abortion to occur. Application of this model demonstrates the risk of a spontaneous abortion is twice as likely in occupational workers whose fetal radiation doses are closer to the maximum allowable limit of 5mSv compared with those who maintain fetal radiation doses below 1mSv