The positive signs of pregnancy are those objective signs referable to the fetus appearing after the quickening, any one of which can definitely establish the diagnosis of pregnancy. They become positive only when elicited by the examining physician, to wit: (1) the fetal heart tones, heard by the physician; (2) fetal movement, felt by the physician, and (3) fetal parts palpated and differentiated by the physician. Some of the recent textbooks, such as that of De Lee, mention roentgen-ray examination of the fetal skeleton in the last trimester as an additional sign, but place very little emphasis on its value or range of usefulness. A final sign, the presence of chorionic villi in uterine scrapings, is also a positive sign, but obviously does not concern us in this presentation.
Granted that the fetal roentgenogram is a positive sign, what is its practical value? Several articles have appeared on this subject
STEIN IF, ARENS RA. ROENTGENOGRAMS OF THE FETAL SKELETON AS A POSITIVE SIGN OF PREGNANCY. JAMA. 1923;81(1):4-8. doi:10.1001/jama.1923.02650010008002