A calm, safe approach to the baby whose sex isn't clear at birth - and the emergency hiding behind it.
CASE · THE CALL
You're paged to the postnatal ward. A term baby, born to a G2P1 mother after an uncomplicated pregnancy. The midwife is flustered: "I've examined the baby and... I genuinely can't tell you if it's a boy or a girl. The parents keep asking."
Before you walk in: what is your first move, and what will you say to the parents?
WHY THIS MATTERS
Two things are happening at once
A sensitive moment
Sex is the first thing every family is asked. Getting it wrong - or guessing - causes real, lasting distress. This is a situation to handle calmly, honestly and without assigning a sex until you know.
A hidden emergency
The commonest cause is congenital adrenal hyperplasia (CAH), which can cause a salt-wasting crisis and cardiovascular collapse in the first weeks of life. The genitals are the clue; the adrenal gland is the threat.
The rule that keeps babies aliveAmbiguous genitalia is congenital adrenal hyperplasia until proven otherwise - it is the diagnosis that can kill.
FIRST PRINCIPLES
The calm approach
Don't guess a sex. Don't complete the birth certificate. Use neutral language - "your baby" - and tell the family honestly that the genitals haven't finished developing the way we'd expect, that this needs some tests and the right specialists, and that you'll support them throughout. Then work the problem systematically: is this a virilised female, an undervirilised male, or a mix?
60-SECOND REFRESHER
How sex develops - and where ambiguity comes from
Every early fetus has a bipotential gonad and both duct systems. Which way it goes depends on a chain of signals - and ambiguity is a mismatch somewhere along that chain.
Bipotential gonad + both duct systemsWolffian (male) & Müllerian (female) ducts are both present in every early fetus
↓ Is SRY present? (the testis-determining gene on the Y chromosome)
So: a 46,XX fetus exposed to excess androgen virilises (→ looks more male), and a 46,XY fetus that can't make or respond to androgen under-virilises (→ looks more female). That is the whole of ambiguous genitalia in one sentence.
ASSESSMENT
History and examination
History
Antenatal: maternal virilisation (acne, hirsutism), scan-predicted sex vs appearance, maternal hormones/medications, and any NIPT or antenatal karyotype result (NIPT is now routine and increasingly flags sex-chromosome discordance, e.g. 45,X/46,XY).
Openings - one urogenital opening or separate; urethral position (glanular → perineal).
Labioscrotal folds - degree of fusion, rugosity, pigmentation.
Prader staging - the spectrum of virilisation
1
Clitoromegaly only
2
+ partial labial fusion
3
Single urogenital sinus; more fusion
4
Phallic urethra; near-fused, scrotum-like
5
Male-appearing; impalpable gonads
↔
A continuum, not boxes
FEMALE-TYPICALMALE-TYPICAL
Figure slot
THE TWO PEARLS THAT DECIDE EVERYTHING
It all comes down to the gonads
Pearl 1A palpable gonad is a testis until proven otherwise. Ovaries and streak gonads don't descend - so a palpable gonad means testicular tissue is present (~75% of 46,XY DSD have palpable gonads). Palpable gonad(s) → think 46,XY DSD (or ovotesticular).
Pearl 2 · the dangerous oneBilaterally impalpable gonads in an apparently male newborn = a virilised female (CAH) until excluded. In all virilising CAH the gonads are impalpable - and CAH is the one that can crash.
Our baby has impalpable gonads, a 46,XX karyotype and a uterus on ultrasound - a virilised female. CAH from 21-hydroxylase deficiency causes ~95% of CAH and is the commonest cause of ambiguous genitalia.
The block, and why it virilises
21-hydroxylase deficiency - the enzyme blockcortisol and aldosterone can't be made; everything above the block backs up
17-OHP ↑ (the test) → shunted into androgens → virilises the 46,XX fetus
The emergency · salt-wasting crisis~75% of classic CAH is salt-wasting. Aldosterone deficiency causes renal salt loss, typically presenting in the first 1-3 weeks (often days 4-15) with poor feeding, vomiting, weight loss, dehydration and shock. Biochemistry: ↓Na⁺, ↑K⁺, metabolic acidosis, hypoglycaemia.
The trap: girls are flagged early by the ambiguous genitalia - but boys look normal and can present collapsed at 1-2 weeks of age. Keep CAH on the list for any unwell, dehydrated, hyperkalaemic neonate.
Managing the crisis
Step
What to do
Resuscitate
IV 0.9% saline bolus for shock; treat hypoglycaemia (IV glucose) and hyperkalaemia.
Glucocorticoid
IV hydrocortisone (stress dose) - replaces cortisol; at stress doses also gives some mineralocorticoid effect.
Mineralocorticoid + salt
Fludrocortisone and sodium chloride supplements once established (oral).
Bloods first if possible
Take 17-OHP, electrolytes, glucose, cortisol, ACTH, renin before steroids - but never delay treatment in a crisis.
Involve
Paediatric endocrinology early; CAH is also on the newborn screening (17-OHP).
THE WORK-UP
A first-day approach
Send a focused first-line panel, then let the karyotype and 17-OHP steer you down one of three branches.
Sex-chromosome DSD. e.g. 45,X/46,XY mixed gonadal dysgenesis.
Reading the cluesA uterus on ultrasound means AMH was low (a Sertoli-cell / testis problem); a palpable gonad with ambiguity means androgen action was insufficient. Hormones are most informative during mini-puberty (until ~4 months), and gene panels increasingly give a confirmed diagnosis. Any Y material (e.g. gonadal dysgenesis) carries a gonadoblastoma risk - flag for surveillance.
Don't forgetWhile the work-up runs, monitor electrolytes and glucose daily for at least the first 1-2 weeks - the salt-wasting crisis can arrive after you've stopped worrying.
THE FRAMEWORK
Classifying DSD (Chicago consensus, 2006)
What actually causes ambiguous genitalia: CAH accounts for over half (>50%); sex-chromosome DSD / gonadal dysgenesis for ~35-40%; the rest (mostly 46,XY DSD) are each rare. So step one is always to exclude CAH.
Terminology: the 2006 Chicago consensus introduced "DSD" and retired terms like "pseudohermaphroditism". Usage keeps evolving - many now prefer "differences of sex development", and many affected people and communities use "intersex" or "variations in sex characteristics". Follow the family's lead, describe the findings plainly, and avoid imposing a label.
CASE B · A DIFFERENT TRAP
A "baby boy" is referred to you with severe (penoscrotal) hypospadias and bilateral impalpable gonads. The night RMO has already congratulated the parents on their son.
Why should that pairing stop you in your tracks?
Hypospadias + bilateral undescended/impalpable gonads is a DSD until proven otherwise - never just a urology referral. By Pearl 2, impalpable gonads in an "apparently male" baby could be a virilised CAH female. Here the karyotype returns 46,XY, the gonads are found in the inguinal canals, and testosterone/AMH are present → a 46,XY DSD (e.g. partial androgen insensitivity or 5α-reductase deficiency). Same calm approach; same MDT.
MANAGEMENT
The team, and the decisions
DSD is managed by a specialist multidisciplinary team: neonatology, paediatric endocrinology, paediatric urology/surgery, clinical genetics, psychology and social work. Your job as the registrar is to stabilise (think CAH), investigate, communicate, and refer - not to decide the diagnosis or the sex of rearing alone.
Do not assign a sex or register the birth until the MDT has assessed
Sex of rearing is a considered, parent-involved MDT decision
It weighs karyotype, anatomy, likely function/fertility and hormone responsiveness
Irreversible early surgery is increasingly deferred - shared decision-making, specialist centres only
Keep monitoring for salt-wasting throughout
Arrange psychological support for the family early
Rights, ethics & the modern approachThe strong current direction - clinically and in human-rights frameworks - is shared decision-making with the family and deferring irreversible, non-essential genital surgery until the child can take part, except where it is medically necessary. References: Darlington Statement (Australian/Aotearoa intersex consensus, 2017) · UN OHCHR: intersex people · Global DSD Update 2016.
Nursing considerations
Use neutral, non-gendered language; do not guess or assign a sex - say "your baby".
In suspected CAH, monitor electrolytes, glucose, feeding and weight for salt-wasting; escalate signs of adrenal crisis.
Protect privacy and confidentiality; document sensitively.
Support parents - this is distressing; keep communication consistent and involve them.
TALKING TO PARENTS
What to say - and what not to
✓ Do
Say "your baby" - never "it".
Be honest: "Your baby's genitals haven't finished developing the way we'd expect. We need some tests and the right specialists before we can tell you more."
Acknowledge it's hard, and that you'll support them.
Reassure that this is uncommon but well-understood, and there's a clear plan.
✗ Don't
Guess the sex ("it's probably a girl").
Complete the birth certificate or announce a name/sex.
Use stigmatising words (intersex, hermaphrodite) with the family.
Rush, or sound alarmed - calm, plain language reassures.
TAKE-HOME
If you remember five things
Ambiguous genitalia is CAH until proven otherwise - it's the one that can kill.
A palpable gonad is a testis; bilaterally impalpable gonads in an "apparently male" baby = a virilised female (CAH) until excluded.
CAH (21-hydroxylase) → ↑17-OHP, and salt-wasting (↓Na, ↑K, acidosis, hypoglycaemia) in the first 1-3 weeks - boys are the trap.
Don't assign a sex or register the birth - stabilise, investigate, involve the MDT.
Communicate calmly: "your baby", honesty, and support.
Discussion questions
1
A term "boy" collapses at day 10 with Na⁺ 122, K⁺ 7.1 and glucose 1.8. What's your differential and your first three actions?
2
The parents ask "but is it a boy or a girl?" on day 1. Word your reply.
3
Which single examination finding most changes your differential, and why?
4
Why is hypospadias with bilateral undescended testes never "just hypospadias"?
Related
This page is part of the Endocrine & Metabolic teaching series.
CAH (coming soon)Neonatal hypoglycaemia (coming soon)← All systems