Antenatal diagnosis of genetic disease / edited by A.E.H. Emery.

Date:
1973
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Antenatal diagnosis of genetic disease / edited by A.E.H. Emery. Source: Wellcome Collection.

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    amniocentesis: technique and complications 17 the same patient in whom the placenta has already been localized, this may be done in a separate room set aside for the purpose. Technique of Amniocentesis after 20 Weeks Gestation Placentography, as a preliminary, may be done using ultra¬ sonography, radioisotopes such as Cr^i (Bowman and Pollock, 1965), radioiodinated serum albumen (Hibbard, 1966) or soft tissue placentography (Free and McDonnell, 1970). Freda (1965, 1966, 1967) and Crystle and Rigsby (1970) have used a combina¬ tion of techniques involving radioisotopes and thermography. Placentography is particularly indicated in obese patients. These techniques will at least give a guide as to where the bulk of the placenta lies and on some occasions the actual margin of the placenta may be delineated. Amniocentesis can then be done in an area where the placenta is absent. The patient should empty her bladder before lying as comfort¬ ably as possible on a firm couch. A brief explanation of the procedure is again made, and the lower abdomen then exposed. The height of the uterine fundus is noted, and palpation of the fetus carried out to find in particular the area in which the limbs are lying or whether the presenting part can be eased out of the brim of the pelvis to allow access to this region (Fig. 2 a and в). Queenan (1967) advocates insertion of the needle in the area of the fetal neck posteriorly where there is usually a good-sized pool of hquor. Haworth, Milic and Adamsons (1968) found that by using the suprapubic region in more than 6000 consecutive punctures no complications were attributable to the direct effect of amnio¬ centesis, and they felt it unnecessary, using this technique, to perform placentography. Wiklund (1969) also advocated the suprapubic approach. In the final analysis, the site chosen will depend on the experience of the operator and on where he feels he can confident¬ ly obtain a clear specimen of liquor with minimal trauma to mother and fetus. The fetal heart should then be checked, maternal venous blood taken for fetal cell count and the aseptic ritual adhered to. Using a fine needle the skin is infiltrated with local anaesthetic and with a 21 gauge needle the infiltration is continued down to the level of the peritoneum. Freda (1965) points out that if the uterus contracts either in toto or at the point where the needle is being inserted, then the sensation on penetration of the uterine wall is more difficult to assess; for this reason, it is better not to