If doctors suspect hemophilia A or B in a young child, they will do some simple lab tests. They will take a blood sample, and measure the amount of factor VIII and factor IX in the blood.
The tests will show:
Hemophilia A and B can be divided into three classifications.
|CLASSIFICATION ||LEVEL OF FACTOR VIII |
OR IX IN THE BLOOD
|Severe ||Less than 1% of normal |
|Moderate ||1 to 5% of normal |
|Mild ||5 to 30% of norma|
One of the lab tests will show how much von Willebrand factor (VWF) is in the blood. Von Willebrand factor is another of the proteins in the blood which is important for normal clotting. It acts as a glue, sticking platelets to the wall of a broken blood vessel. If the level of VWF is low, then the person has von Willebrand disease, not hemophilia A or B.
It usually takes 1 to 2 weeks for test results to come back.
Yes, there are several options.
Attitudes about hemophilia often depend on personal experience. Some carriers have grown up with a close relative who has complications from the disease. They could belong to a family with inhibitor problems. They might have seen the consequences of HIV or hepatitis C in a loved one. They may have witnessed the pain caused by joint disease. They feel the need for alternatives to having a child with hemophilia. Religion, personal values and culture also play a part in decision-making around prenatal diagnosis and termination of pregnancy. Couples should work closely with the hemophilia treatment team and genetic counsellors throughout the prenatal diagnostic process for both medical and emotional support.
Some couples choose not to have prenatal diagnosis (PND) and simply want a male baby tested at birth. Others, in order to prepare themselves, feel they need to know the hemophilia status, even if they have no intention of terminating the pregnancy.
Other couples are interested in prenatal diagnosis because terminating the pregnancy if the baby has hemophilia—as hard as that decision may be for them—is an option. Precautions must be taken when terminating a pregnancy, as with any surgical procedure, to avoid bleeding complications. The hemophilia treatment team must be involved in preparations and follow-up. Following a termination, counselling should be offered to help couples cope with the emotional strain.
The genetic counselling session should be tailored to support the personal values and beliefs of the family so that the couple feel secure in whatever decision they make. The objective of prenatal diagnosis is to try and provide carriers and their spouses with accurate and current information so they can make an informed decision in a supportive environment. Genetic counsellors protect the couple’s autonomy and confidentiality, and provide support and education. They must be sensitive to the range of values, cultures, religious beliefs and ethnic differences in our society. In this way, individuals or families can make decisions that are in keeping with their value and belief systems.
Obligate carriers or potential carriers of hemophilia (for example, a case of no family history but a son already born with hemophilia) are eligible for prenatal diagnosis. If available in a laboratory in the province where the family resides, the procedure is covered by provincial health insurance. Otherwise, a special request to the provincial Ministry of Health may need to be made to cover the cost of out-of-province testing.
Prenatal diagnostic options
Some couples find out the sex of the baby by ultrasound and then make a decision about invasive testing only if the ultrasound predicts the baby to be a boy. The sex can generally be predicted by ultrasound at 16 weeks gestation. Couples should be informed of the limitations of ultrasound in predicting the sex of the baby.
Figure 8 from p.65 of AAC
Chorionic villus sampling (CVS)
The chorion is a membrane that surrounds the developing foetus. It is located outside of the amniotic membrane. The chorion is a foetal membrane, that is to say, it originates from the same cells as the developing baby. The chorion is covered with finger-like projections called chorionic villi. In early pregnancy, the villi will implant in the uterus at one point to develop into the placenta, and the remainder of the villi disappear. CVS can be carried out after 11 weeks gestation to obtain DNA for analysis. The sample may be taken either by the vaginal or abdominal route, depending on where the placenta is located.
Figure 9 from p. 65 of AAC
Vaginal CVS is similar to a pap smear. While an ultrasound is being done on the abdomen to locate the foetus, a speculum is inserted into the vagina. A fine tube is then passed through the cervix and guided to where the placenta is forming. About 10 to 15 milligrams of tissue are aspirated into a syringe. Results can take up to 3 weeks. The abdominal method is similar to amniocentesis. CVS is avoided before 11 weeks because of reports of limb abnormalities occurring when carried out earlier. The miscarriage rate associated with this procedure is approximately 1%. CVS is covered by provincial health insurance.
Amniocentesis is done after 15.5 weeks. An ultrasound is performed to locate the placenta and to select a pocket of amniotic fluid. A thin needle is then inserted through the abdomen and into the uterus. A small amount of amniotic fluid is removed. This fluid contains cells that the foetus has shed. In some circumstances, the cells need to grow before the DNA from them can be extracted. The risk for complications with the procedure is 0.5%. Test results take 3 to 4 weeks if cells need to be grown before the test can be done. Amniocentesis is covered by provincial health insurance.
The difference between amniocentesis and CVS is that CVS is done much earlier in pregnancy and thus the results are received earlier.
As with any medical procedure in a carrier of hemophilia, precautions must be taken to avoid bleeding complications. Couples should work closely with the hemophilia treatment team, including the obstetrician and genetic counsellors throughout the process for medical and emotional support, including follow-up.
Foetal blood sampling
Foetal blood sampling may be carried out at 18 weeks or more gestation. A sample is taken from the umbilical vein, under ultrasound guidance, through a needle inserted into the abdomen. Blood is taken, and the factor level can be assayed immediately. It is important to ensure that the sample in the tube is truly foetal blood and not maternal. A difficult procedure, the risk of miscarriage is as high as 5%.
Maternal blood test
A new non-invasive method for prenatal diagnosis is at present being developed. In future, a blood sample taken from the mother at 7 to 8 weeks gestation will be tested for foetal blood cells. The foetal male chromosomes will be separated from the mother's blood and tested for hemophilia. This procedure is still in development.
Potential psychosocial issues at prenatal diagnosis
If a carrier already has a brother or son with hemophilia and the results from prenatal diagnosis show that the baby is a boy and has hemophilia, she may feel ambivalent about stopping a pregnancy, as she dearly loves her son or brother. By stopping a pregnancy when the baby is predicted to have hemophilia, she may feel like she is rejecting her son and/or brother. On the other hand, she may not know whether she can emotionally handle having another child with hemophilia. Her own feelings may conflict with those of her partner.
These are examples of the psychosocial issues that often come up in a genetic counselling session. A genetic counsellor explores these feelings with the couple. This may take more than one counselling session.
In the context of hemophilia, the number of women seeking PND in the developed world seems to be decreasing with the successful use of prophylactic treatment. Prophylactic and on-demand home care has improved the quality of life for young people with hemophilia and their families, allowing most to grow up without severe joint disease or other complications. A study in Sweden showed the main reasons carriers do not use prenatal diagnosis is that they do not consider hemophilia to be a disorder serious enough to justify termination of a pregnancy. Having a child, however, is a personal decision and each woman has the right to choose what's best for her and her family. Previous personal experience of hemophilia is still the greatest contributing factor affecting decisions.