Abstract: Objective To investigate the values of P450 oxidoreductase (POR) gene test by amniocentesis for prenatal diagnosis in a pregnant woman whose husband had a heterozygous mutation in POR gene. Methods In this case report, the abnormal pregnant history in mother and genitalia deformities in her fetus were described. POR gene from the woman and her husband was tested by PCR. During her second pregnancy, the cells from amniotic fluid were collected for POR gene test. The external genitalia and bone status was evaluated after the baby was born. Results 1) the woman presented excessive virilization, such as deepen voice and facial acnes, during her first pregnancy. Her baby twins, manifesting elbow osseous fusion, clitoridauxe and cerebral palsy, died 2 weeks after birth. 2) A heterozygous mutation in POR gene (G1370A, Arg457His) was revealed in the peripheral blood cells from her husband. 3) During her second pregnancy, amniocentesis was conducted and POR gene test for cells from amniotic fluid was negative. 4) A female baby was born uneventfully with normal external genitalia and bone status. Conclusions POR gene test in amniotic fluid can provide important information for prenatal diagnosis.

Key words: P450 oxidoreductase deficiency, Ambiguous genitalia, Osseous fusion abnormality, Prenatal diagnosis