Reduction of Fetal Irradiation in Pelvimetry

With the growing concern regarding possible hazard to the fetus resulting from irradiation during gestation, it has become increasingly apparent that more attention to the fetal dose delivered during pelvimetry is indicated. Studies by Stewart et al., Lewis, and others (1–3) suggest an increased incidence of neoplasia in children who have received radiation in utero incident to pelvimetry. The significance of these data is not yet documented, and it may prove that no actual relationship exists. However, the general awareness of the public and the nonradiologist physician requires that the radiologist direct his attention to this matter. Both parents and physicians have expressed increasing concern in this respect and demonstrated a real reluctance to accept Pelvimetric examination because of possible radiation hazard to the unborn child. The two possible solutions of the problem are to omit pelvimetry altogether or to take steps that will radically reduce the fetal exposure. In the conventional examination, as done in most institutions and radiological offices, no attempt has been made in the past to spare the fetus. In the triangulation method (5, 6) two 14 × 17-inch roentgenograms are obtained, with the fetus usually receiving total-body irradiation (Fig. 1). The dose received in connection with these two projections has been variously estimated at from 1,600 to 9,000 milliroentgens (4). The justification for this type of examination has been that one can gain information as to fetal position and station, presence or absence of multiple pregnancies, and possible fetal anomalies. Actually, however, in only a fraction of pregnancies has pelvimetry been done, and only a small segment of the fetal population has been so evaluated. By far the majority of pregnancies are carried through to term without this information being available or needed. It is believed that the slight gain provided could well be dispensed with if we could thus drastically reduce fetal exposure. In the author's experience in several thousand cases he has failed to find that a knowledge of the fetal head size has significantly altered the prognosis from the Pelvimetric standpoint. Such knowledge he has used solely for assessment of fetal age when information on this point was needed in the presence of some condition requiring premature induction of labor or in explanation of what appeared to be a prolonged period of gestation. For this reason, it is felt that one can dispense with any information regarding the fetal head without significant detriment to the pelvimetry study. In the few instances where specific information as to fetal head size or relation of the fetal head to the pelvis is required, the examination can be altered accordingly.