Helpline 0300 111 4748

KS/XXY for Families to be

Klinefelter’s Syndrome (KS)/XXY is a common congenital condition (that means it is present at birth).

It is found in around 1 in 600 live male births and is caused by the presence of one or more additional sex chromosomes.

If you have been told that the baby you are expecting is likely to have Klinefelter’s Syndrome (KS)/XXY, you have come to the right place for reliable information and friendly support.

This section of the website is especially for you. When you are ready for more information there is lots more to explore.

If you would like to know about another parent’s experience, please read   

 Catherine’s story.

KS/XXY has a very wide range of possible effects, and the severity  varies considerably from person to person.

However we do know that early diagnosis and appropriate support can make a huge difference, so your baby will be one of the lucky ones.

The extra X can come from either parent. It occurs by chance and isn’t because of something which you have – or haven’t done. 

Chromosomes are genetic material. Males typically have one X and one Y chromosome (XY) and females have two X chromosomes (XX). People with KS have two X chromosomes and one Y chromosome (XXY). This is why the KSA refers to the condition as KS/XXY.

KS/XXY is diagnosed by a genetic blood test which identifies the karyotype i.e. the number, size and shape of the chromosomes.

Although the condition is relatively common, its effects are not well understood. Many members of the medical profession still think it is very rare and may be dismissive. Remind them that KS/XXY affects 1 in 600.

Prenatal screening

Prenatal diagnosis


Puberty and beyond


Useful links

If you would like to talk to someone please call our Helpline:

0300 111 47 48.

Please remember that as the KSA is run entirely by volunteers. Sometimes there may not be anyone available to take your call. Please leave a message with your email address or phone number and we will get back to you.


If you are feeling suicidal,  please contact the Samaritans
They are available 24 hours per day, phone: 116 123 or visit