Prenatal diagnosis: detailed chromosomal analysis in 500 cases

Natural history of trisomy 18 and trisomy 13: I. Growth, physical assessment, medical histories, survival, and recurrence risk

The natural history of trisomy 18 and trisomy 13 was investigated using data derived from parent questionnaires and medical records from 98 families with an index case of trisomy 18 and 32 families with an index case of trisomy 13. Data are presented on pregnancy, delivery, survival, medical complications, immunizations, growth, cause of death, cytogenetics, and recurrence risk. Half of the trisomy 18 babies were delivered by C-section. Fetal distress was a factor in half, and the only reason in a third of C-section deliveries. One minute Apgar scores were significantly lower in C-section and breech deliveries. There were more small for gestational age babies than in the general population, but most of the low birth weight newborns were small for gestational age, unlike the general population. Survival in this group of children was better than in other studies due to ascertainment bias. There were more girls than boys at all ages for both conditions, and the sex ratio decreased with time. Growth curves for length, weight, head circumference, and weight vs height are provided. Long-term survival did not appear to be due to mosaicism. We found no adverse reactions attributable to immunizations. At age 1 year there was an average of approximately 2 operations per living child. We report the second case of successful major cardiac surgery in a trisomy 18 child. Almost 70% of deaths were attributed to cardiopulmonary arrest. The sibling recurrence risk for trisomy 18 or trisomy 13 was 0.55%.

Temporal changes in Ohio amniocentesis utilization during the first twelve years (1972-1983), and frequency of chromosome abnormalities observed

The history of amniocentesis utilization in the seventh largest state of the United States is documented from its inception in 1972 through the first half of 1984. Amniocentesis utilization ratios for Ohio residents aged greater than or equal to 35 have increased from 0.21 per cent (19/9091) in 1972 to 23.4 per cent (1655/7531) in 1983, representing an average annual growth rate of 43.1 per cent. Of the amniocenteses performed from January 1, 1978-July 1, 1984, 71 per cent were referred for advanced maternal age (greater than or equal to 35), 15 per cent for maternal anxiety (30-34), 10 per cent for family history or previous child with a genetic defect, and 4 per cent for other reasons. Between 1978-1983 utilization by women 45 years of age was only 20 per cent higher than women 35 even though their risk of giving birth to a Down syndrome child was bout one order of magnitude higher. In addition, various factors were tested as to whether they affected utilization of amniocentesis by women greater than or equal to 35 during 1978-1983. A strong correlation of +0.89 existed between county population size and utilization ratios. No difference in utilization was found between whites and nonwhites, regardless of county population size. When utilization ratios were compared separately between Protestants, Catholics and other religions in Ohio's most populated county, no statistical differences were found. From 1978-July 1, 1984, the frequency of all cytogenetically abnormal chromosome results observed in Ohio amniocenteses to women greater than or equal to 35 was 2.48 per cent (187/7536). Of these, 2.15 per cent (162/7536) had unbalanced karyotypes. Future maximum amniocentesis utilization for women greater than or equal to 35 is estimated at 60-70 per cent.

Familial occurrence of chromosome 7/12 translocation

A new balanced translocation, t(7;12) (p12;p13), was found in a high genetic risk family in which the mother is a translocation carrier. She had 12 pregnancies, six of which were terminated during the first trimester by spontaneous abortions. Among the six live births, three children inherited the translocation from their mother and were phenotypically normal. The father and three other children had normal karyotypes.

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.

Hazards of amniocentesis: an unidentifiable fragment

A 38-year-old woman had amniocentesis performed for advanced maternal age. The karyotype of the cultured amniotic fluid cells showed a minute fragment in all cells analyzed, 47,XY+Fg. The fragment could not be identified. For medical reasons the pregnancy had to be terminated at 34 weeks. Both skin and blood cultures from the aborted fetus showed a 47,XY,21+ karyotype.