Prenatal diagnosis is usually offered to help with reproductive planning and risk assessment.
If you know that haemophilia runs in your family, you may wish to have a test during pregnancy to find out the sex of your baby.
Free foetal DNA (ffDNA) is a blood test arranged by your haemophilia centre to find out the sex of your baby during the early stages of pregnancy. As early as nine weeks of pregnancy cells from your baby (foetal cells) can be detected in your blood and these are analysed to work out the baby’s sex. The test results take about a week and your haemophilia centre will contact you as soon as they have the results. If you don’t want to know the sex of your baby your haemophilia centre can still do the test but inform your obstetric team without telling you the results. At this stage, some women will choose not to continue their pregnancy, this should be discussed with the haemophilia doctor.
If you are carrying a male foetus, you may then choose to have a test called chorionic villus sampling (CVS). CVS is a test where the doctor takes a sample of cells from the placenta. It is usually carried out between 11 and 14 weeks of a pregnancy. To do the test, the doctor puts a fine needle through the wall of your abdomen or a thin tube into your vagina and up into the womb. They can then take a small sample of cells from the placenta for genetic testing.
An additional possible test is amniocentesis. This means taking a sample of fluid from the womb, from inside the membrane holding the baby. The fluid contains cells from the baby that can be genetically tested. Amniocentesis is usually done later in pregnancy than CVS, from between 15 and 20 weeks until near the end of pregnancy.
There is a risk of miscarriage with CVS and amniocentesis tests – about 1 in 100. Your doctor will talk you through all the possible risks and what the test can show before you decide whether you want to go ahead.
Management of care for all pregnant carriers should involve close cooperation between the haemophilia and obstetric teams. It is important to have a clear plan for delivery that is shared with the mother to be and kept in her medical notes
More information is available in our Understanding Haemophilia booklet.