Carrying the haemophilia gene

Carrying the haemophilia gene

Last reviewed: July 2013

Many girls or women who carry the altered factor VIII or IX gene causing haemophilia (the "haemophilia gene") do not have symptoms of a bleeding disorder. If at least one of their X chromosomes has a factor VIII or IX gene that works, their body can usually produce normal or near normal levels of factor and they do not have bleeding problems.

However, some girls and women who carry this gene may have a bleeding tendency. They are often described as “symptomatic carriers”. If their factor levels fall in the range for mild haemophilia (5 – 40% of normal clotting factor), they may sometimes also be referred to as having “mild haemophilia”. In very rare cases, some girls or women have particularly low factor levels causing them to have moderate or severe haemophilia.

Examples of having a bleeding tendency or symptoms may include:

  • Bruising easily
  • Heavy menstrual bleeding. This may lead to low iron levels or anaemia
  • Excessive bleeding after dental surgery or extractions, other surgery and medical procedures, injuries or accidents
  • Prolonged bleeding after childbirth
  • Females with very low clotting factor levels may also have joint or muscle bleeds.

All females who carry the gene should have testing for their clotting factor levels.

Unlike males with haemophilia, where the factor level is the same within the same family, the factor level in females who carry the gene is unpredictable and varies between family members.

Women and girls with lower levels should have theirs checked periodically, as their factor levels may change with age, pregnancy and hormonal medications. If their factor level is low, they will need a treatment plan to prevent bleeding problems and manage any situations that occur.


Genetic testing

Family planning




Important Note: This information was developed by Haemophilia Foundation Australia for education and information purposes only and does not replace advice from a treating health professional. Always see your health care provider for assessment and advice about your individual health before taking action or relying on published information.

This information may be printed or photocopied for educational purposes.

Last Updated: 8th Apr 16