AMNIOGRAPHY IN THE DIAGNOSIS OF FETAL DEATH.

Abstract

Establishing the diagnosis of intrauterine fetal death is not an uncommon problem in medical practice. The absence of fetal movements and the inability to hear fetal heart tones are only presumptive evidence of fetal death, and present-day conventional abdominal radiography yields reliable conclusions in only 50 per cent of cases (2–4, 9, 14, 19). The purpose of this article is to reintroduce a safe, accurate, easily performed technic, amniography, and to discuss its role as a highly reliable test of fetal death. The Normal Amniogram The technic of amniography has previously been described in detail by McLain (16, 17) and will be reviewed only briefly here. The patient is given 1 cc of a contrast medium, for example 75 per cent Hypaque, intravenously as a test dose. If no untoward reaction occurs she is instructed to empty the bladder, the anterior abdominal wall is prepared, and local anesthesia is given. An 18-gauge spinal needle is then inserted 3 to 4 ern below the umbilicus in the midline through the anterior abdominal wall into the amniotic sac. If the placenta is encountered, the puncture should be performed elsewhere, although transplacental injection has occurred on several occasions with no unusual problems encountered in either the mother or fetus. When the amniotic sac is entered, approximately 35 to 40 cc of fluid is withdrawn and the same amount of contrast medium is injected. Adequate time is allowed for mixing. Radiographs are taken according to the type of information sought. Usually a one-hour and a three-hour film in the frontal or lateral projection are sufficient for determination of fetal death. The gastrointestinal motility of the fetus in both normal and abnormal pregnancies has been studied previously (16, 17) and is summarized in Table I. The normal fetus begins to swallow the contrast material almost immediately. In a fetus of thirty-six to forty weeks gestation serial radiographs reveal the material in the stomach within five to fifteen minutes, in the small bowel in fifteen to thirty minutes (Fig. 1), and in the colon by five to seven hours (Figs. 2–5). The rate of swallowing and motility varies with gestation, being quite prolonged in younger fetuses. As the fetal age increases, motility becomes more rapid, ultimately reaching the predictable values which are given in Table I. The inability of a dead fetus to swallow radiopaque amniotic fluid within a reasonable time represents the basis upon which amniography is employed in the diagnosis of fetal death. We have accepted one to three hours as the time expected for a fetus of any age to show some contrast material within the gastrointestinal tract. If none is seen on these radiographs, a six-hour delayed film is obtained. If the gestation is less than thirty weeks, a twenty-four-hour film should also be taken. Should this roentgenogram also fail to demonstrate ingested contrast material, the diagnosis of fetal death can be made with certainty. Such conditions as hydramnios, fetal hydrops, and certain severe congenital anomalies of the fetus may delay the passage of contrast material through the gastrointestinal tract, but will not cause a complete lack of ingestion (Fig. 6) (16, 17).