• ambiguous genitalia
• intersex

• AMH, anti-Müllerian hormone
• CAH, congenital adrenal hyperplasia
• DHEA, dehydroepiandrosterone
• DHEAS, dehydroepiandrosterone sulphate
• DHT, dihydrotestosterone
• EUA, examination under anaesthesia
• hCG, human chorionic gonadotrophin
• StAR, steroidogenic acute regulatory protein

To discover that there is uncertainty about the sex of one’s newborn baby is devastating and often incomprehensible for most parents. It is paramount that clear explanations and investigations are commenced promptly, and that no attempt is made to guess the sex of the baby. Extreme sensitivity is required, and ideally the baby should be managed in a tertiary centre by a multidisciplinary team including a paediatric endocrinologist and a paediatric urologist. Early involvement of a clinical psychologist with experience in this field should be mandatory. Other professionals including geneticists and gynaecologists may also become involved. There must be access to specialist laboratory facilities and experienced radiologists. The incidence of genital ambiguity that results in the child’s sex being uncertain is 1 per 4500,¹ although some degree of male undervirilisation, or female virilisation may be present in as many as 2% of live births.²

Parents require reassurance that either a male or female gender will definitely be assigned. However the outcome of some of the investigations may take some weeks, and registration of the child’s birth should be deferred until gender has been assigned. This may require communication with the Registrar of Births, and a skilled clinical psychologist will help the parents in deciding what to tell family and friends in the interim. It is also helpful (if appropriate) to reassure the parents that their child is otherwise healthy.

While not all intersex conditions are apparent at birth (for example, complete androgen insensitivity may only become apparent in a child with a testis within an inguinal hernia, or at puberty with primary amenorrhoea and lack of androgen hair), only those presenting with genital ambiguity at birth will be considered in this article.

An understanding of sex determination and differentiation is essential to direct appropriate investigations …