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Androgen insensitivity syndrome (AIS) is sometimes diagnosed soon after a baby is born, although often it's not noticed until a child reaches puberty.

Doctors may suspect AIS based on a child's appearance and sexual development, but some tests will be needed to confirm the diagnosis.

Appearance and sexual development

Partial androgen insensitivity syndrome (PAIS) is usually spotted soon after birth because the genitals have an unusual appearance.

Complete androgen insensitivity syndrome (CAIS) isn't usually diagnosed at birth because the genitals look normal for a girl, but the condition may be picked up if the child gets a hernia.

Hernias are where an internal part of the body pushes through a weakness in the surrounding tissue. They can occur in babies with CAIS if the testicles fail to move from the tummy into the scrotum.

When the baby has an operation to repair the hernia, the surgeon may find the testicles inside the hernia or in the tummy, and tests may be arranged to check for CAIS.

If a baby with CAIS doesn't develop a hernia, the condition may go undiagnosed until puberty, when she doesn't start having periods and doesn't develop pubic and underarm hair.

Read more about the symptoms of AIS and types of AIS.

Tests and scans

If AIS is suspected, blood tests can be used to:

  • check the sex chromosomes – sex chromosomes are bundles of genetic material that determine a person's genetic sex; if their genetic sex is different from their physical appearance, they may have AIS
  • check for a genetic fault – AIS is caused by a problem on the X chromosome, the sex chromosome a child with AIS receives from their mother
  • measure sex hormone levels – children with AIS tend to have high levels of testosterone (the male sex hormone) in their blood

An ultrasound scan can also be used to confirm the absence of the womb and ovaries. Children with AIS often have female genitals, but no female internal reproductive organs.

If a surgeon thinks they've found testicles in a baby's tummy during a hernia repair operation, a small tissue sample (biopsy) may be taken and analysed to confirm they are testicles and not ovaries.

Testing family members and unborn babies

If someone in your family has AIS and the specific genetic fault causing it has been identified, it may be possible to have a blood test to check if you carry the same fault and are at risk of passing it on to any children you have.

Testing can also be carried out in unborn babies when there's a known family history of AIS.

There are 2 main tests that can be carried out during pregnancy to determine whether a baby has the condition:

  • chorionic villus sampling (CVS) – a sample of cells are removed from the afterbirth (placenta) for testing, usually with a needle; this is usually carried out between week 11 and week 14 of pregnancy
  • amniocentesis – a needle is used to extract a sample of the fluid surrounding the baby (amniotic fluid) for testing; this is usually carried out between week 15 and week 20 of pregnancy

It can be difficult to decide whether or not to have these tests, so it's a good idea to speak to a genetic counsellor first.

It's also important to be aware that the risk of miscarriage after CVS and amniocentesis is estimated to be about 0.5 to 1%. This means 1 in every 100 to 200 women will have a miscarriage after having CVS or amniocentesis.