March 5, 2008
Research: Causes and Prevention
Question from Israel:
I am a father of a type 1 diabetic daughter who has had diabetes since the age of six. Recently, she asked me about the risk of her future kids having diabetes. I read on The Genetics of Diabetes page at the ADA web site that "If you are a woman with type 1 diabetes and your child was born before you were 25, your child's risk is 1 in 25; if your child was born after you turned 25, your child's risk is 1 in 100." Should I interpret this as a recommendation for my daughter to have her babies only after she is 25? I also read that a test of the HLA-DR genes of an embryo may provide a projection for the risk of a child to become diabetic. Putting all the moral and religious questions aside, is this test is something that people in the U.S. or other locations tend to do and act on?
I went to the ADA web site and reviewed the page about genetics and diabetes. I sent the ADA an e-mail asking for clarification about the risk to a mother with diabetes of having children with diabetes (either a reference or an explanation of the finding). I have not yet heard back from the ADA. This does not imply that one should wait until after 25 to have children. In fact, the risk to the mother of complications during pregnancy is also associated with the duration of disease.
I have yet to have a patient who has had HLA typing of the embryo for risk for diabetes. This is possible with pre-implantation genetic diagnosis in an IVF clinic. I am not aware of anyone terminating a pregnancy due to a potential risk for diabetes in the child. Also from the ADA page is an interesting observation: in identical twins with increased risk for diabetes and one with diabetes, there is still only a 50% chance that the other twin will develop diabetes. The comment is that there is an environmental factor involved in the process as well.
Additional comments from Dr. Jim Lane:
Although I do not have statistics available to me that will answer your question directly, I work with a lot of families where the parents have type 1 diabetes. It is my feeling that the state of the art includes prenatal counseling with a perinatologist who has familiarity with managing the pregnancies of women with type 1 diabetes. I do not think that it is popular to have HLA typing on the fetus for the purpose of determining risk of type 1 diabetes. After all, even if they have the genes, it does not say they will get the disease.
The issue of the timing of pregnancy is a complicated one and I think it should be discussed in the presence of a specialist. There are times when a couple may want to have their family earlier, rather than later, because the mother may already have some diabetes-related complications that would most likely get worse over time.
Additional comments from Dr. Stuart Brink:
Genetic testing for diabetes is sill a research issue in the U.S. and all around the world. The risk for your daughter having a child with diabetes is approximately 2 to 5%. So, if you are an optimist, that means 95 to 98% of children of a women with type 1 will NOT have diabetes. This is obviously higher than the general population where the risk of type 1 diabetes is in the neighborhood of 1:600 in the U.S. The risks in Israel are somewhat lower as they are in other Mediterranean area countries.