X-ray exposure in utero and school performance : a population-based study of X-ray pelvimetry

Aim To investigate the association between exposure to ionising radiation from pelvimetric examinations in utero and school performance. Material and methods This was a population-based cohort study comprising 46,066 children born in the county of Ostergotland, Sweden, from 1980 through 1990. Through record linkage between Swedish registers, children exposed in utero to X-ray pelvimetry examination were compared to other children born in the same county during the study period, as well as to their unexposed siblings. Outcome variable was primary school grades, expressed in centiles and calculated through linear regression. Results In the univariate analysis, children exposed to X-ray pelvimetry in utero had higher school grades compared to unexposed children (point estimate 3 centiles, 95% confidence interval [CI]: 1.5 to 4.6). When sex, mother's education and income, birth order, and birth position were included in the analysis; however, the difference was reduced and the association was no longer statistically significant (PE 1.4, 95% CI: –0.1 to 2.8). Comparing exposed children with their siblings showed no statistical difference in univariate analysis or in multivariate analysis. Conclusion No suggestion was found of a negative effect on school performance from in utero exposure of diagnostic X-ray pelvimetry.