Diagnosis is by testing the blood for its ability to clot and its levels of clotting factors.Prevention may occur by removing an egg, fertilizing it, and testing the embryo before transferring it to the uterus. Human embryos in research can be regarded as the technical object/process. Missing blood clotting factors are replaced to treat haemophilia. This may be done on a regular basis or during bleeding episodes. Replacement may take place at home or in hospital. The clotting factors are made either from human blood or by recombinant methods. Up to 20% of people develop antibodies to the clotting factors which makes treatment more difficult. The medication desmopressin may be used in those with mild haemophilia A. Studies of gene therapy are in early human trials.Haemophilia A affects about 1 in 5,000–10,000, while haemophilia B affects about 1 in 40,000, males at birth. As haemophilia A and B are both X-linked recessive disorders, females are rarely severely affected. Some females with a nonfunctional gene on one of the X chromosomes may be mildly symptomatic. Haemophilia C occurs equally in both sexes and is mostly found in Ashkenazi Jews. In the 1800s haemophilia B was common within the royal families of Europe. The difference between haemophilia A and B was determined in 1952. Signs and symptoms
Characteristic symptoms vary with severity. In general symptoms are internal or external bleeding episodes, which are called "bleeds".
Before pregnancy
Genetic testing and counselling are available to help determine the risk of passing the condition onto a child. This may involve testing a sample of tissue or blood to look for signs of the genetic mutation that causes haemophilia. During pregnancy
A pregnant woman with a history of haemophilia in her family can test for the haemophilia gene. Such tests include:

chorionic villus sampling (CVS): a small sample of the placenta is removed from the womb and tested for the haemophilia gene, usually during weeks 11–14 of pregnancy
amniocentesis: a sample of amniotic fluid is taken for testing, usually during weeks 15–20 of pregnancyThere is a small risk of these procedures causing problems such as miscarriage or premature labour, so the woman may discuss this with the doctor in charge of her care. After birth
If haemophilia is suspected after a child has been born, a blood test can usually confirm the diagnosis. Blood from the umbilical cord can be tested at birth if theres a family history of haemophilia. A blood test will also be able to identify whether a child has haemophilia A or B, and how severe it is. Classification
There are several types of haemophilia: haemophilia A, haemophilia B, haemophilia C, parahaemophilia, acquired haemophilia A, and acquired haemophilia B.Haemophilia A is a recessive X-linked genetic disorder resulting in a deficiency of functional clotting Factor VIII. Haemophilia B is also a recessive X-linked genetic disorder involving a lack of functional clotting Factor IX.