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The most important pelvic diameter from the point of view of the obstetrician is the true conjugate. It can be measured either from the outside or from the inside. The external measurements are seldom reliable, as from them the internal pelvic diameter can be calculated only indirectly. The internal measurement of the true conjugate, either by digital vaginal examination or by means of the Bilicki-Gauss internal pelvimeter, although quite reliable in experienced hands, is most disagreeable to the patients, is not always devoid of danger, and cannot be carried out when the head is engaged in the pelvic brim. The transverse diameter cannot be measured directly either externally or internally. The radiological examination of the pelvis has therefore become an extremely valuable factor in obstetric diagnosis, as it allows exact measurement of the pelvic canal at any time during pregnancy without the slightest risk or discomfort to the patient. The first radiography of the pelvis was performed by Varnier and C...

These measurements should be taken as early in pregnancy as possible as it is then much easier to get a distinct and complete outline of the pelvic brim. In the later months it is much more difficult and throws a greater strain on the apparatus and tube. A. A “hatchet.” This is a piece of thin sheet lead, supported between layers of ply-wood, and shaped as shown. It is free to rotate at the end of a handle about eighteen inches long. Its concave portion is used to shade off the anterior portion of the patient's body during the radiographic exposure, as described later. B. A pair of obstetric callipers. C. A strip of lead, called a “rule,” about twelve inches long and two wide, supported by ply-wood. It has small holes drilled down the centre, exactly half-an-inch apart. From this “rule” the “pubic scales,” Fig. 2, are made in the following way. The “rule” is supported horizontally over the Potter-Bucky four and three-quarter inches above the surface, a film in a cassette being placed in the usual position...

A method of pelvimetry is described which is recommended for standardisation. Two radiographic views are required, three if the pelvic outlet is to be measured. Only two measurements are recorded by the radiographer. No calculations are necessary. Procedure.—Metal calipers are applied to the pelvis in the manner suggested by Hederman (1940): (a) At the level of the pelvic brim in Thoms' position (a special manoeuvre ensures that the obstetric conjugate is horizontal). (b) In the sagittal plane. The anode-film distance is not critical. The caliper measurement is recorded in each instance. The “pelvimetry protractor” is constructed from a rectangular sheet of perspex. It bears a centimetre scale from each division of which lines are engraved which radiate uniformly. A cursor thread with sliding hooks may be moved up and down parallel to the scale. Mode of use.—Two radiating lines are chosen according to the recorded caliper measurement by reference to the basal centimetre scale. The protractor is placed ove...

Some time ago I evolved the following technique for radiographic pelvimetry, because I found that each of the existing methods had certain disadvantages in practice. Chief of these are the following: 1. The majority of my cases are sent towards full term with a request for a report on the position, presentation, and full pelvic measurements. Now in order to estimate the position, two views are normally required: antero-posterior and true lateral, while the customary methods of X-ray pelvimetry require a semi-recumbent attitude of the patient. These are all of necessity exposures requiring a large intensity of radiation. It therefore became apparent that some method of obtaining pelvic measurements from the ordinary antero-posterior and lateral views was to be desired. 2. I had always used Thoms' method in preference to the others, but it seemed that one could never be sure that the perforated metal sheet was in the exact plane previously occupied by the pelvic brim, especially in obese patients. The metho...

In an excellent recent article (Dunster et al., 1976) comparison was made between the ultrasonic and isotopic methods of localizing the placenta. Although not disagreeing for one moment with the authors' eventual conclusion that the ultrasonic method was preferable, perhaps two other factors should be considered. Firstly, the lower segment cannot be regarded as “an area within 5 cm of the internal cervical os”. In a 20-week pregnancy, the lower uterine segment hardly exists at all and yet by the time labour commences at term it may include the whole area of the uterus between the internal os and the pelvic brim, rather, more than 5 cm.