Further observations of true mosaic trisomy 17 ascertained in amniotic fluid cell cultures.

Three new cases of true mosaic trisomy 17 (MT17) were diagnosed in amniotic fluid cells. Postnatal chromosome analysis from lymphocytes did not confirm the trisomic cell line, and follow-up studies showed normal psycho-motor development of the children, in one case up to the age of 4 1/2 years. We suggest that there are similarities between MT17 and MT20, in which the majority of pregnancies result in deliveries of healthy babies.

On the significance of true trisomy 20 mosaicism in amniotic fluid culture.

Nine new cases of prenatally detected true mosaic trisomy 20 (T20) are reported. In three instances the fetuses were aborted. One fetus showed multiple malformations associated with a high percentage of T20 cells among amniotic fluid (AF) cells and fibroblasts of different fetal tissues. In two other fetuses only a slight facial dysmorphy was seen which was accompanied by a low percentage of T20 cells among AF cells. In five instances the pregnancies were carried to term, and normal somatic and psychomotor development of the children has been observed, in one case up to the age of 24 months. In one case the pregnancy is continuing. The T20 cells were not detected among cultured lymphocytes of these children. A review of the hitherto known cases of prenatally detected mosaic T20 indicates a relationship between the prenatal findings and the fetal development. This may serve as a provisory basis for genetic counselling: in the case of a percentage above 50% of T20 cells among AF cells there seems to be a risk of about 50% for the fetus to be affected by severe anomalies. However, in cases of a prenatally detected mosaic T20 with a percentage equal to or less than 50, fetal or congenital malformations have not been observed among 23 individuals so far examined.

[Gynecological aspects of prenatal diagnosis of congenital anomalies (author's transl)]. / Gynäkologische Aspekte der pränatalen Diagnostik angeborener Anomalien

In the light of our own observations, the technique of amniotic fluid puncture in early pregnancy is described, the risk of the procedure to the mother and child is set forth and further responsibilities are explained. Two indication groups predominate: pregnant women of older maternity age and women who have already given birth to a child presenting Down's syndrome. As can be derived from the figures, all gynecologists nowadays must include the possibilities of prenatal recognition of congenital anomalies in family planning and maternity care. An anomaly can be excluded in about 95% of potential genetic risk pregnancies.