Your question is an important one. In order to answer it accurately, there are a number of important considerations. The answer may be different for each couple and would depend on the exact type of muscular dystrophy you have. In general, it would be important for you to be seen and assessed by a genetic counsellor or medical geneticist who would be able to assess your personal history, family history and what genetic testing is required, and then provide you with available options for both assessing the risk and preventing your child from having the same condition.
Muscular dystrophies are a large diverse group of inherited conditions. They may be inherited in different ways. This so-called pattern of inheritance would determine whether or not your child is at risk. In some cases, a condition is present in a number of family members. In this case the pattern of affected individuals may allow a geneticist to determine the risk to your child (even without further testing). In others, an individual may be the only one with the condition in the family, or the pattern may not be so clear. In these cases, genetic testing may be necessary to identify the precise genetic fault causing the disease in an individual and the risk that other family members or a child could be affected. Thus, once an affected individual is diagnosed in a family, it is essential that the exact genetic condition be defined and, ideally, the genetic fault identified. This allows for a family to be given precise information as to who else is at risk and exactly what the risks are, as they vary considerably in different conditions. Testing to identify a disease-causing fault can be time consuming and must be performed prior to planning a pregnancy.
In a family in which a muscular dystrophy is identified and a future child is at risk, the disease can be prevented in future pregnancies in a number of ways. A family that wishes to explore these options needs to consult with a geneticist to discuss which options are most suitable to their exact situation. They also need to make informed choices as to which options are correct for them as a family. For example, a couple may choose to avoid the biological risk by adopting an unrelated child, or a donor egg or sperm could be used to prevent the faulty gene from being transmitted.
An at-risk couple could also choose to test an at-risk conceptus. This testing can be performed only if the exact disease-causing genetic fault in the family has been identified prior to a pregnancy, so that testing in a pregnancy would be more efficient and streamlined, as there are time constraints. Testing an at-risk conceptus can be done in two ways:
- Prenatal testing can be performed on an at-risk established pregnancy. A sample can be obtained from the fetus by either chorionic villus sampling (CVS) at approximately 12–14 weeks of pregnancy or by amniocentesis at 16–18 weeks. This material can be tested for the family-specific genetic fault, and this information can be used to accurately determine if the pregnancy is affected or not. If the fault is not identified, a couple can be reassured of a healthy outcome. If predicted to be affected, medical termination of pregnancy can be offered.
- Preimplantation genetic diagnosis can also be offered. Here a couple would need to go through in vitro fertilisation (IVF) using their own sperm and eggs. Embryos are created in the laboratory and then tested for the family-specific genetic fault. Once this is done, healthy embryos can be implanted in the woman’s uterus to achieve an unaffected pregnancy. Embryos with the genetic condition are not implanted.
Newborn screening is not routinely available in South Africa and would not detect most muscular dystrophies, as they are diverse and rare. Screening is typically offered where there is no known family risk. It would not be appropriate for determining whether a newborn with an affected family member has muscular dystrophy. However, if a newborn is known to be at risk, for example because a parent is affected, specific testing could be done at birth to determine if the baby is affected or not.
There have been many recent genetic advances, and there is hope for the future that new gene therapies may be able to cure some genetic diseases, if affected embryos or newborns are diagnosed early enough. These options are, however, not yet available. There are many technical and ethical challenges that remain before such therapies become available to at-risk couples.
The determination of risk to an embryo or newborn is complex. It is strongly recommended that a geneticist be involved in the process to ensure that timely and accurate options are offered. The options available for each couple need to be individualised on the basis of the couple’s preferences, the genetic risk and the genetic testing available.