Two unique patients with trisomy 18 mosaicism and molecular marker studies.

We report two unusual patients with trisomy 18 mosaicism presenting with minor anomalies and failure to thrive in the first year of life. Chromosome analysis showed trisomy 18 in 30/30 peripheral blood lymphocytes in both children. Analysis of skin fibroblasts in the first child showed normal female chromosomes in 30/30 cells, and the fibroblast karyotype in the second child showed mosaicism for tetrasomy 18p, trisomy 18, and normal female chromosomes (karyotype 47,XX, +i(18)(p10)[47]/47,XX, +18[9] /46,XX[4]). Trisomy 18 commonly results from nondisjunction at maternal meiosis II (MII). Nondisjunction at maternal MII has also been postulated to be the initial step in the formation of tetrasomy 18p. In our second case, the additional chromosome 18 was the result of maternal nondisjunction at MII, consistent with this hypothesis. In the first case, nondisjunction at maternal meiosis I (MI) was responsible for the extra chromosome 18.

Fetal sympatho-adrenal mediated metabolic responses to parturition.

Plasma cortisol and noradrenaline were measured in 15 mothers and babies following vaginal delivery and in 17 following elective caesarean section and related to blood concentration of glucose and glycerol. Significant elevations in umbilical artery cortisol and noradrenaline concentration were found in the vaginal delivery group. Blood glucose and glycerol concentrations were significantly higher in the vaginal delivery group for maternal venous, umbilical artery and vein samples. However, when allowances were made for placental transfer of these substances, little evidence was found to support sympatho-adrenal mediated mobilization of glycerol and glucose in the fetus. The possible explanation for the apparent dissociation between marked sympatho-adrenal activity and metabolic responsiveness during parturition in the fetus is discussed.