Clinical overview
A newborn with ambiguous genitalia is simultaneously a potential medical emergency, a diagnostic puzzle, and a profoundly sensitive family situation — and the assessment must hold all three at once. The emergency is salt-wasting congenital adrenal hyperplasia (CAH), the commonest cause, which can kill in the first fortnight of life; the puzzle is the structured work-up that establishes the underlying difference (disorder) of sex development (DSD); and the sensitivity is that a family is waiting to be told "is it a boy or a girl?" while you must counsel them honestly that the answer needs time and a team. This objective is to demonstrate the assessment, so the chapter is weighted toward the history, the examination, the investigations and the multidisciplinary process — and toward the communication that must run alongside them.
Two rules anchor the approach. First, do not assign or register a sex hastily — a wrong, irreversible declaration causes lasting harm; sex of rearing is decided by an experienced multidisciplinary team after investigation, with the family. Second, exclude salt-wasting CAH urgently in every case, because it is both the most likely diagnosis and the most lethal if missed. The chapter uses the modern, respectful DSD terminology (which replaced "intersex"/"hermaphrodite") and links to hyperandrogenism (the shared 21-hydroxylase biology), informed-consent (the consent and communication imperative), and principles-of-inheritance.
Core knowledge
Terminology and classification (Chicago Consensus)
Figure E2.1 — The DSD classification (Chicago Consensus), anchored on karyotype: sex-chromosome DSD, 46,XX DSD (androgen excess — commonest is CAH), and 46,XY DSD (under-virilisation).
The 2006 Chicago Consensus (Lawson Wilkins Paediatric Endocrine Society + ESPE) introduced "differences/disorders of sex development (DSD)" — congenital conditions in which development of chromosomal, gonadal or anatomical sex is atypical — and a karyotype-anchored classification (updated by the 2016 Global DSD Update):
- Sex-chromosome DSD — e.g. 45,X (Turner), 47,XXY (Klinefelter), 45,X/46,XY (mixed gonadal dysgenesis), 46,XX/46,XY chimerism.
- 46,XX DSD — usually androgen excess virilising a genetic female; CAH is by far the commonest (see below). Also maternal androgen sources (luteoma, exogenous), aromatase deficiency.
- 46,XY DSD — usually under-virilisation of a genetic male: disorders of testis development (gonadal dysgenesis), of androgen synthesis (5α-reductase deficiency, 17β-HSD), or of androgen action (androgen insensitivity syndrome), and LH/hCG receptor defects.
Congenital adrenal hyperplasia — the one you must not miss
Figure E2.2 — CAH, the one not to miss: the 21-hydroxylase block shunting precursors to androgens (virilised 46,XX, raised 17-OHP) and the salt-wasting neonatal emergency to treat before results.
21-hydroxylase deficiency accounts for the majority of CAH and is the commonest cause of ambiguous genitalia. The enzyme block diverts steroidogenesis away from cortisol (± aldosterone) toward androgens, so:
- A 46,XX infant is virilised (clitoromegaly, labial fusion, a common urogenital sinus) — ambiguous genitalia in a genetic female with normal ovaries and uterus and impalpable gonads.
- 17-hydroxyprogesterone is markedly raised (the diagnostic test).
- The salt-wasting form (aldosterone deficiency) causes an adrenal crisis from about day 3–14 — hyponatraemia, hyperkalaemia, hypovolaemia, hypoglycaemia, shock — which is the lethal emergency. (A 46,XY infant with CAH has normal-appearing male genitalia and presents only with the salt-wasting crisis — easily missed.)
The single most useful examination finding
Palpable gonads. A gonad palpable below the inguinal ring is almost always a testis (or ovotestis) and therefore implies Y-chromosome material — it is essentially never an ovary. Conversely, bilaterally impalpable gonads with virilised genitalia point to a virilised 46,XX infant — i.e. CAH until proven otherwise. This one finding orients the entire differential.
Assessment
Figure E2.3 — The structured newborn assessment: stabilise first, the palpable-gonad rule, Prader staging, parallel investigations, urgent MDT, and do NOT assign/register sex before expert review.
History
- Antenatal/birth: maternal virilisation or androgen exposure in pregnancy, antenatal scan findings, prematurity.
- Family history: consanguinity (recessive CAH and others), previous neonatal/unexplained infant deaths (undiagnosed salt-wasting CAH), known DSD, infertility or "amenorrhoea" in relatives (clues to AIS).
- The pregnancy and any discordance between antenatal predicted sex and the appearance at birth.
Examination
- General/neonatal: hydration, blood pressure, signs of evolving salt-wasting crisis, dysmorphic features or other anomalies (syndromic DSD), hyperpigmentation (ACTH excess in CAH).
- Genital examination, systematically:
- Gonads — palpate the labioscrotal folds and inguinal canals; symmetry and palpability are the key data (see above).
- Phallus — stretched length and width; degree of virilisation graded by the Prader scale (I–V) from mild clitoromegaly to a fully formed phallus with a penile urethra.
- Urethral/vaginal openings — separate openings vs a single common urogenital sinus; position of the meatus (hypospadias).
- Labioscrotal folds — degree of fusion and rugosity; symmetry (asymmetry suggests differing gonads, e.g. mixed gonadal dysgenesis).
- Document objectively with diagrams; avoid premature gendered language.
Investigations (urgent, in parallel)
- Karyotype (with rapid QF-PCR / FISH for X and Y / SRY for a fast answer).
- 17-hydroxyprogesterone (the key test for 21-hydroxylase CAH) — interpret after ~day 2 to avoid the physiological neonatal peak.
- Serum electrolytes, glucose and a blood gas, monitored serially from day 3 — to detect salt-wasting before collapse.
- Testosterone, and the testosterone:DHT ratio (5α-reductase deficiency), androstenedione, 17-OHP and a steroid profile; ACTH/renin/aldosterone; AMH and inhibin B (presence of functioning testicular tissue).
- Pelvic/abdominal ultrasound — presence of a uterus and Müllerian structures, gonadal position, and adrenal size.
- hCG stimulation test (testicular androgen synthesis), urogenital sinogram/examination under anaesthesia to map the anatomy, and targeted molecular genetics as the picture narrows.
The multidisciplinary process and communication
- Refer urgently to a specialist DSD multidisciplinary team — paediatric endocrinology, paediatric surgery/urology, clinical genetics, neonatology, psychology and (in SA) social work; tertiary-centre care.
- Communication: tell the family honestly and compassionately that the baby's genitals have not developed in the usual way and tests are needed to understand why before the sex of rearing is decided — avoid guessing, avoid "intersex"/old terms, use the baby's name and neutral language, and give consistent messages. Support the family and protect privacy.
- Sex of rearing is a considered MDT-and-family decision informed by diagnosis, anatomy, likely gender identity, fertility and functional prognosis; irreversible surgery is deferred/individualised in line with contemporary, rights-aware practice — not a hasty neonatal procedure.
Management (assessment-stage principles)
- Treat the emergency first: a salt-wasting crisis needs resuscitation, IV hydrocortisone, fluids/glucose, and correction of hyponatraemia/hyperkalaemia — do not wait for the karyotype.
- Establish the diagnosis through the parallel work-up above, coordinated by the MDT.
- CAH maintenance: glucocorticoid (± mineralocorticoid/salt) replacement, sick-day rules, long-term endocrine follow-up.
- Surgical and psychological care: individualised, MDT- and family-led, with deferral of irreversible procedures where appropriate.
- Genetic counselling for recessive conditions (CAH) and recurrence risk (principles-of-inheritance).
Red flags / pitfalls
- Missing salt-wasting CAH — the lethal trap; check electrolytes serially from day 3 and treat a crisis empirically; remember a 46,XY CAH baby looks like a normal boy and presents only with collapse.
- Assigning/registering a sex before investigation — irreversible harm; defer to the MDT.
- Calling a palpable gonad an "ovary" — a palpable gonad implies a testis/ovotestis and Y material until proven otherwise.
- Interpreting a single 17-OHP taken too early — avoid the physiological neonatal peak (recheck after ~day 2).
- Using outdated, stigmatising terms ("intersex", "hermaphrodite", "true/pseudo") with the family — use DSD terminology and the baby's name.
- Managing in a non-specialist setting — this needs an experienced DSD MDT at a tertiary centre.
- Forgetting the family — the psychosocial and counselling needs are part of the assessment, not an afterthought (informed-consent).
Evidence anchors
- Chicago Consensus on management of intersex/DSD (Lee, Hughes et al.; LWPES + ESPE, 2006) and the Global DSD Update (Lee et al., 2016) — DSD terminology and karyotype-based classification.
- Endocrine Society Clinical Practice Guideline — Congenital Adrenal Hyperplasia due to 21-Hydroxylase Deficiency (Speiser et al., 2018) — diagnosis (17-OHP), salt-wasting recognition, and glucocorticoid/mineralocorticoid management.
- Prader staging of external genital virilisation.
- South African context — tertiary-centre MDT DSD care; CAH newborn screening is not universal in SA, so clinical vigilance for the salt-wasting crisis is essential; genetic counselling and social-work support.