Prenatal chromosome determination. A study of 219 cases

Factors affecting the success of mid-trimester amniocentesis

Of 298 women who had mid-trimester amniocentesis carried out in a single hospital unit in a 6-yr period, an increasing proportion were carried out for detection of neural tube defects. A clinical decision could be made following the first amniocentesis in 77% of cases. There were 16% where liquor was not obtained at the first attempt, and a further 7% where cell growth or biochemical testing was unsatisfactory. The outcome was influenced by the experience of the operator and timing of procedure. The success of the first procedure was 59% before 16 wk of gestation and 86% between 16 and 20 wk. The incidence of blood-staining of the liquor was higher with an anterior placenta (19%). Despite difficulties, the abortion rate (3.5%) does not appear to be higher than would be expected.

Fetal-maternal hemorrhage after amniocentesis: incidence, degree and ramifications

A review of the literature indicates a small but significant incidence of fetal-maternal hemorrhage following amniocentesis. In these studies, consideration has not been given to the frequency with which erythrocytes containing hemoglobin F are to be found in the maternal circulation in the absence of amniocentesis. In this investigation, Kleihauer-Betke analysis was carried out before and after amniocentesis. This study confirms previous reports that spontaneous fetal maternal hemorrhage is not uncommon during normal intrauterine gestation and that amniocentesis is probably only an occasional cause of fetal-maternal hemorrhage. This impression is based on the findings that most Kleihauer-positive maternal blood samples after amniocentesis were also positive before amniocentesis. In spite of these findings, and since Rh-immune serum globulin is apparently harmless to the fetus and mother, its use is still advocated in nonsensitized Rh-negative mothers after amniocentesis.

Prenatal cytogenetic diagnosis: first 1,000 successful cases

From February 1969 to August 1976, we studied 1,048 amniotic fluids. Of these, 958 (91.4%) were primarily for prenatal cytogenetic diagnosis. Cytogenetic studies were attempted in 1,021 cases; the diagnosis was successful in 1,000 of these. The failure rate of obtaining a diagnosis from the amniotic fluid cell culture of the first amniocentesis was 5% (50 cases); 29 cases had a repeat tap and successful diagnosis was achieved in all. In 21 cases, a repeat tap was refused. Thus, the overall failure rate of obtaining a final cytogenetic diagnosis was 2.06% (21/1,021). There were 32 fetal losses after amniocentesis including 16 spontaneous second trimester abortions, 7 fetal deaths in utero and 9 stillbirths. In two additional cases, fetal death had occurred before amniocentesis. This number of fetal losses does not exceed the number that would be expected in the same maternal age group without amniocentesis. In our series, the frequencies of trisomy in maternal age groups 40 years and over, 37-39 years, 35-36 years, and under 35 years were 4.5, 3.14, 0 and 0% respectively. These frequencies are comparable to those reported from other prospective prenatal studies and higher than those of retrospective live born studies. Various problems and pitfalls in prenatal cytogenetic diagnosis are discussed.

Prenatal diagnosis of genetic disorders

Three hundred and fifty pregnancies were monitored by transabdominal amniocentesis in the fourteenth to sixteenth week of gestation followed by karyotyping or biochemica assays of cultured amniotic fluid cells and analysis of alpha-fetoprotein in the amniotic fluid supernatant. The pregnancy was interrupted in 36 cases (10%) either becasue of a fetal abnormality or the presence of a male fetus in pregnancies at risk for an X-linked disease. Four chromosomal aberrations were found in 87 pregnancies tested because of advanced maternal age. In 101 pregnancies with a recurrence risk of Down's syndrome, 2 fetuses with an abnormal karyotype were detected. In 11 cases, in which 1 parent was a carrier of a balanced translocation, 2 unbalanced fetal karyotypes were found. Fetal chromosome studies in 43 pregancies at risk for an X-linked disease indicated the presence of a male fetus in 21 cases. Prenatal diagnosis of 11 different metabolic diseases was performed in a total of 34 cases. Microchemical techniques were used to allow completion of the diagnosis of seven different enzyme deficiencies within 9 to 22 days after amniocentesis. Alpha-fetoprotein assay in the amniotic fluid supernatant of 47 pregnancies at risk for an open neural tube defect resulted in the detection of 3 anencephalic fetuses during the second half of pregnancy. The safety and reliability of amniocentesis and the possible effects on the outcome of pregnancy are evaluated. Prenatal diagnosis offers a promising alternative for parents who are at risk of having a child with a genetic disease which can be detected in amniotic fluid or in cultured amniotic fluid cells.