Amniotic fluid testosterone concentration as an index of fetal sex.

Abstract

Summary: Testosterone concentrations were measured by radioimmunoassay in 57 amniotic fluid samples obtained from 43 women whose gestational ages varied from 14–40 weeks. These women were grouped according to the sex of the fetus and the gestational age at the time of amniocentesis: group I, less than 20 weeks; group II, 21–30 weeks; group III, 31–40 weeks. In each gestational age group, mean testosterone concentrations were significantly higher in women bearing male fetuses. Of the 14 patients comprising group I, 8 bore male fetuses. The mean testosterone concentration for male fetuses in this group was 198.7 pg/ml (range 93–319.8 pg/ml) and 74.1 pg/ml for female fetuses (range 39–122.8 pg/ml). Group II was comprised of 23 patients, 13 of whom bore male fetuses. The mean testosterone concentration for male fetuses was 221.5 pg/ml (range 133.6–395.0 pg/ml), and for female fetuses it was 67.7 pg/ml (range 35.6–103.0 pg/ml). Group III consisted of 20 patients of whom 10 bore male fetuses. The mean testosterone concentration for the male fetuses was 149.1 pg/ml (range 99.2–262.0 pg/ml), and for female fetuses it was 60.2 pg/ml (range 39.5–96.7 pg/ml). Some overlapping of individual testosterone values was observed in fluid from male and female fetuses; however, the percentage of women bearing males and having amniotic fluid testosterone concentrations greater than 100 pg/ml was 93.5% (29/31). The percentage of women bearing females with testosterone concentrations less than 100 pg/ml was 88.5% (23/26).Speculation: Amniotic fluid testosterone concentrations have proven useful for the antenatal diagnosis of fetal sex. Correlation between the fetal sex based upon testosterone analysis and the amniotic fluid karyotype increases the probability that the cultured cells are of fetal origin. Certainty of diagnosis could be increased even further by combining antenatal sex diagnosis with fluorescent Y-chromatin screening of uncultured amniotic fluid. A combination of these techniques should aid in the elimination of diagnostic errors arising from contamination by maternal cells.