RT Book, Section A1 Bianchi, Diana W. A1 Crombleholme, Timothy M. A1 D'Alton, Mary E. A1 Malone, Fergal D. SR Print(0) ID 1106399668 T1 Ambiguous Genitalia T2 Fetology: Diagnosis and Management of the Fetal Patient, 2e YR 2015 FD 2015 PB McGraw-Hill Education PP New York, NY SN 978-0-07-144201-5 LK obgyn.mhmedical.com/content.aspx?aid=1106399668 RD 2024/12/11 AB Key PointsIncidence is 1 in 5,000 livebirths. Most common cause is congenital adrenal hyperplasia (CAH), resulting in a virilized genetic female. This autosomal recessive condition has an incidence of 1 in 14,000 livebirths.Prenatal classification of ambiguous genitalia is based on cause. Fetuses can be virilized genetic females, undervirilized genetic males, or true hermaphrodites with both ovarian and testicular tissue present.Sonographic prenatal diagnosis of ambiguous genitalia is more accurate in males. Clitoromegaly is associated with false-positive diagnosis in females. The presence of a normal fetal uterus after 19 weeks is strongly predictive of a virilized genetic female.Differential diagnosis in a virilized female includes androgen exposure due to CAH or maternal tumors. An undervirilized male may be due to defects in the synthesis of testosterone or its precursor, androgen insensitivity, chromosome abnormalities, or true hermaphroditism. Single-gene disorders, such as Smith–Lemli–Opitz syndrome, should be considered.Prenatal management should include fetal karyotype and testing of 7-dehydrocholesterol (7-DHC) levels in the amniotic fluid. Delivery should occur at a tertiary center.Fetal treatment is available for CAH and Smith–Lemli–Opitz syndrome.Infant sex assignment should occur after birth using a team approach.The role of genital surgery in children with ambiguous genitalia is controversial.Recurrence risk depends on the etiology of the ambiguous genitalia.