The Interpretation of Early Fetal Roentgenograms

Abstract

In this communication we wish to discuss the interpretation of early fetal roentgenograms exclusive of those after pneumoperitoneum. In an article published in the Journal of the American Medical Association, July 7, 1923, we considered the importance of the roentgenogram showing the fetal skeleton as a positive sign of pregnancy. In the former we primarily considered the fetus from mid-pregnancy to term, while it is our desire at this time to emphasize the possibility of depicting the fetus as early as possible and to describe the findings thus obtained. The problem of producing a satisfactory film in the early period, one that has a real interpretive value from a roentgenographic as well as a diagnostic standpoint, is a vastly different one than at a later period of fetal development. It is our aim to show some definite evidence of fetal bony structure at the earliest possible moment, in order to make a positive diagnosis, and we are not especially concerned at this time with the position of the fetus. Quoting from our previous paper we regard the “roentgenogram of the fetal skeleton as the earliest demonstrable positive sign of pregnancy.” It has been stated by others that the fetal skeleton can regularly and constantly be depicted on films at three, three and one-half, or four months. As a result of considerable experience, and some experimentation in this period, we are compelled to take issue with this view. It has been in exceptional instances only that we have been able to visualize the fetal skeleton prior to mid-term. Even when a satisfactory film has been secured, one from which positive findings can be obtained, die entire skeletal structure usually cannot be clearly outlined. Only an extremity, a few vertebrae, the head or a part thereof may appear. When the head can be seen it is the occipital bone which is usually observed, and if other cranial bones are also visible, the occiput is always densest. When the fetus happens to lie transversely in the uterine cavity with its back presenting, almost the entire fetal skeleton may be observed on the film. The tilt of the pelvis, the relation of the sacrum to the skeletal shadows, gas and intestinal contents, pelvic contents, all or singly, may offer sufficient resistance to the passage of the rays through the pelvis, so that the resulting conglomeration of shadows wipes out the fetal skeletal shadows on the films. Adequate preparation of the patient to minimize intestinal contents is highly desirable, but frequently is impossible to control. The importance of the position of the patient can again well be emphasized at this time. The uterus, before mid-term, does not rise very high into the abdomen. If the roentgenogram is made in a straight antero-posterior or postero-anterior position, then the fundus which lies below the level of the iliac crests is covered by the shadow of the sacrum with its dense promontory and the fifth lumbar vertebra.