Fetal sex determination from maternal blood at 6 weeks of gestation when at risk for 21-hydroxylase deficiency.

Abstract

21-hydroxylase deficiency can lead to masculinization of female fetuses. Corticosteroid therapy may reduce these effects. When the fetus is male, this approach means that unnecessary treatment, with theoretic side effects, is given until the result of chorionic villus sampling (CVS), a procedure with known risks, is available. A woman was referred for prenatal assessment at 6 weeks' gestation because her first daughter had been born virilized from 21-hydroxylase deficiency. A real-time polymerase chain reaction assay was performed on maternal blood to detect the fetal Y chromosome-associated SRY gene. A positive signal for the SRY gene was observed. The assay was repeated a few days later, and the result was again consistent with a male fetus. Analysis of cell-free fetal deoxyribonucleic acid in maternal plasma for fetal sex determination might reduce the need for corticosteroid administration and CVS in women with fetuses at risk for 21-hydroxylase deficiency.