Value of Lateral Foetography

Abstract

Indications for foetography (plain X-ray examination of the pregnant abdomen) include the diagnosis of pregnancy, the determination of the position of the foetus, the demonstration of multiple pregnancy, the estimation of foetal maturity, the exclusion of foetal abnormality and the confirmation of foetal death (Roberts, 1932). The commonest indication for foetography is the estimation of foetal maturity (Hartley, 1957), and this is the indication in over 80% of the requests for foetography in the X-ray Department of the University Hospital of the West Indies. Foetal maturity in the later months is most accurately estimated by the appearance of ossification centres in the lower end of the femur, indicating a mature foetus, and in the upper end of the tibia, indicating a post-mature foetus (Adams, 1957 ;Hartley, 1957;Murdoch and Cope, 1957 ; Schreiber, Nichols and McGarrity, 1963), although recently some doubt has been placed on the value of these signs (Dee, Parkin and Simpson, 1966). However, it is still essential in foetography to demonstrate the knees of the foetus clearly.Routine foetography in the University Hospital of the West Indies consisted of a standard postero-anterior view (P.A.) of the abdomen (a postero-anterior view is preferable to an antero-posterior view because of the much lower dose of radiation to the foetal gonads as shown by Clayton, Farmer and Warrick, 1957), which was only supplemented by a lateral view in exceptional cases as recommended by Hartley and Fisher (1955) and Shanks and Kerley (1958). In the postero-anterior view, the knees of the foetus were projected over the maternal spine or pelvis in a large proportion of cases, thereby obscuring details of the ossification centres. As a result it was possible in many cases to make only a crude estimation of foetal maturity.The lateral position in foetography was first introduced by Snow and Powell (1934), and its value was stressed by Hubeny and Delano (1939). I t was noted in many cases examined in this department in which the PA. view had been supplemented by a lateral view that the latter usually demonstrated the knees of the foetus without the superimposition of bony structures of the mother's spine or pelvis. Whilst it would have been possible to take both P.A. and lateral views in every patient referred for foetography (Whitehouse, Simons and Evans, 1958), this was not felt to be justified in view of the radiation hazard to the developing foetus (Vickers, 1965).In view of the problem of the demonstration of the knees of the foetus, it was decided to replace the routine PA. view with a lateral view and only supplement the lateral with a P.A. view in exceptional cases referred for foetography. I t was found that an excellent lateral radiograph of the pregnant abdomen could be obtained in the majority of examinations by using lower exposure factors* than those required for a P.A. radiograph, and it was also found that in the majority of cases the lateral radiograph was more reliable in the estimation of foetal maturity and also gave...