On the basis of a recent national survey, the estimated medical x-ray visit rate during pregnancy was 26 per 100 women. The x-ray experience of pregnant women is significantly less than that of all women between the ages of 15 and 44 in the general population. Of the medical x-ray examinations during pregnancy, approximately 21% occurred during the first trimester, 25% during the second trimester, and 54% during the third trimester. Practically all abdominal examinations related to pregnancy were done during the third trimester, whereas chest and other medical x-ray examinations were more evenly distributed over the three trimesters. Medical x-ray examination rates were highest for primiparous women and for those having high order births.
Brown ML, Roney PL, Gitlin JN, Moore RT. X-ray Experience During Pregnancy. JAMA. 1967;199(5):309-314. doi:10.1001/jama.1967.03120050051009