When a child’s genitals are not easily discernible as either female or male, they are said to have ambiguous genitalia. Most children born with this anatomical abnormality are otherwise healthy, but it can be a scary time for parents. It occurs in about one in every 4,500 newborns, making it hardly rare. There isn’t just one cause.

It can sometimes be quite difficult to determine the gender of the child, but tests can eventually show results.

Ambiguous genitalia is now being referred to more and more as one such Difference (or Disorder) of Sex Development (DSD), which refers to situations whereby a child’s genetics, hormones, internal organs, or external genitalia are atypical.

Normal development of foetal genitalia

When a foetus is developing, the tissue that becomes the gonads – the ovaries or testes – is not differentiated, meaning, it’s all the same, and has the potential to be either ovaries or testes. Because our gender is determined by our father’s sperm (sperm is either a boy or a girl), this is simply in the development of our gender features, not in our gender itself per se, though there is plenty of discussion here for the phenomenon of transgender and mixed gender identity.

This all comes down to genetics – we have 46 chromosomes in every single cell in our body, which equates to 23 pairs. The 23rd pair is used for gender determination, with females having two X chromosomes and males having one X and one Y chromosome.

The presence of the SRY gene causes an undifferentiated gonad to become testes at around the six-week mark of foetal development. Regression, therefore, of the female reproductive tract then occurs in a normal male, causing the formation of the penis, scrotum, and urethra, and later, the descent of the testes into the scrotum.

In a normal female, the absence of the SRY gene causes the gonad to turn into an ovary, and the female reproductive tract continues to develop the uterus and fallopian tubes. The male organs regress.

How does ambiguous genitalia occur?

It is during this process that an unknown genetic blip occurs that influences the development of ambiguous genitals. Other congenital abnormalities may also exist within the same child, though usually the child is otherwise healthy.

What causes ambiguous genitalia?

The cause may not be able to be determined without further testing, since there is a wide variety of conditions that can cause ambiguous genitalia. Sometimes no cause can be found and it is deemed a biological accident.

Children are classified as follows:

Sex chromosome DSD means children who have a mixture of 45 X, 46 XX, 46 XY, and 46 XXY. Some of these kids will have both ovarian and testicular tissue, and both male and female internal organs.


This occurs when the chromosomes are 46 XY, but the testes are undeveloped (gonadal dysgenesis), the right hormones are not produced, or the body either doesn’t respond, or only partially responds, to hormones. There are three conditions to represent these three states: complete androgen insensitivity syndrome, partial androgen insensitivity, and 5-alpha reductase deficiency.

  1. Complete androgen insensitivity syndrome (CAIS) – children who have 46 XY karyotype and normal female external genitalia (does not affect female genitalia, but affects male genitalia)
  2. Partial androgen insensitivity (PAIS) – children who have 46 XY karyotype, with female or male external genitalia, or features of both external genitalia. This condition is also called androgen insensitivity syndrome, since the body does not respond to androgens (testosterone). Mothers with this gene have a 50 per cent chance of passing it on to their daughters.
  3. 5-alpha reductase deficiency (5ARD) – children who have 46 XY karyotype, genital ambiguity, with enzyme 5-alpha reductase being deficient. This enzyme converts testosterone into dihydrotestosterone (DHT), which is necessary to fully complete the masculinisation of a male foetus. Carrier parents have a 12.5 per cent chance of passing it on, since each parent carries a copy of the gene and transmits it to the child.

This combination occurs when babies are exposed to excess male hormones after a malfunction of their own adrenal glands – this is because they have the SRY gene, and have developed testes, but can also occur due to external exposure to male hormones as they are developing in the uterus. This has been up for debate regarding the cause of sexual orientation/preferences and gender identity.

The most common cause of this combination is congenital adrenal hyperplasia (CAH).

Congenital adrenal hyperplasia

Congenital adrenal hyperplasia is one of the more common causes of ambiguous genitals in a child, and must be quickly diagnosed and treated as soon as possible to avoid a very sick baby. It happens in about one in every 15,000 live births.

CAH is caused by a defect in enzyme 21-hydroxylase, a steroid hormone synthesis pathway in the adrenal gland. That sounds a bit like alien-speak, but what it means is there is an issue in creating steroid hormones in the adrenal gland, and this interferes with proper adrenal gland function – testosterone production. Carrier parents have a 25 per cent chance of passing it on to a child.

This can result in girls becoming masculinised and having ambiguous genitalia, but males do not. If the enzyme deficiency is found before or during pregnancy, medication can be given to lessen the effects of the enzyme deficiency if the foetus is female, though this is still experimental.

A second type of CAH is called salt-losing and can be lethal due to blood levels of sodium and potassium changing in the newborn. Treatment is available and lethal outcomes can be avoided if detected early enough. Males and females are equally affected by this type.

Other rare enzyme problems that can result in CAH exist.

Determining gender in children with ambiguous genitalia

First, an examination will be conducted to search for clues. The medical history will include the mother’s pregnancy and any family history of other anatomical abnormalities. Diagnostic procedures can include hormone tests, ultrasounds, and screening for CAH.

Assigning a gender can be complicated without obvious signs, and more so lately than ever, children with ambiguous genitalia can be classified as no gender specifically, and then it usually becomes obvious later on what the child identifies with.

There is much more room for these kids than ever before to be themselves, and not have to have their gender decided for them at an age where it’s impossible to tell, or in fact to have it changed when other signs become more obvious.

The child will need caregivers who can support them psychologically, which is likely to include special support services throughout life.