Every expectant couple–especially if the mom-to-be is over 30–worries about having a child with a genetic disease. That’s why we (or our insurance companies) spend so much money on prenatal testing. In this guest post, Matthew Fickie tackles this issue from two different perspectives. Matt and his wife are both carriers of an abnormal gene for spinal muscular atrophy. He’s also a geneticist.
When my wife and I were trying to conceive a second child I went to an OB appointment with her. After standing silently for half an hour I asked “Should we update our prenatal screening tests?” It’s the sort of question only a medical geneticist asks. But if you’re this geneticist, you carry an abnormal gene for spinal muscular atrophy. That’s not such a big deal, but when my wife also had the abnormal gene, we found ourselves at a 25% risk of having a child who will die the first year of life.
One of the most overlooked but important parts of getting pregnant is prenatal genetic testing. This type of testing looks at your DNA to see if you carry any abnormal genes that, although they don’t cause a disease in you, could cause a disease in your offspring. Here’s how they work: Everyone has 2 copies of each gene, one from mom, one from dad. Some diseases are caused by having just 1 abnormal copy (dominant diseases). Others are caused by having 2 abnormal copies (recessive), and everyone on the planet carries a few of these recessive gene mutations. They don’t cause us any problems unless we hook-up with someone else with the same gene change. This is why you don’t marry your cousins.
Here are some of the most important such tests for Caucasians:
1) Fragile X- this is the number 1 inherited cause of mental retardation. Its inheritance is complex but testing for it has another benefit: Some women carry a “permutation,” that can cause premature ovarian failure. Premature ovarian failure means the ovaries don’t work well and can result in future infertility. In other words, hurry up!
2) Spinal Muscular Atrophy (SMA)- This is the most common genetic cause of death in the first year of life. Babies with this condition die from having low muscle tone. One out of every 50 (2%) of all Caucasians carry the abnormal gene.
3) Cystic Fibrosis (CF)- Children with cystic fibrosis have recurrent lung infections, pancreatic problems, and other medical issues. The treatment for CF keeps getting better but the life expectancy is still only in the late 30’s. Having this gene change is even more common than SMA.
If you are African-American, you should also think about being tested for sickle cell anemia. There are many varieties of this disease so we use a test called “hemoglobin electrophoresis” to look for abnormalities in the structure of hemoglobin that may cause symptoms like anemia or pain.
If you are Ashkenazi Jewish you’ve probably heard of about a disease called Tay-Sachs. Well, there are at least 12 other conditions as bad as Tay-Sachs that are much more common among Jews. It is important to get screened for these conditions even if your partner is a non-Jew.
Here are 3 steps guys can take to help plan for a safe & healthy future pregnancy:
1) Ask your mom: Collect bits of your family history, starting with where your family was from before the United States. See if you have any intellectually disabled uncles or cousins you never knew about and childhood deaths. Here’s a great resource for documenting your family history: https://familyhistory.hhs.gov/fhh-web/home.action
2) Speak up! Very few women know about these tests either so this may be the only time in the pregnancy that you know more than she does. Also, studies show that obstetricians and midwives can be inconsistent in what testing they offer, so be up front about it.
3) Don’t worry! Here’ s the math based on a typical White guy walking into a typical bar and meeting his partner:
Chance that he carries an abnormal CF gene: 1/30
Chance that she carries an abnormal CF gene: 1/30
Combined chance that a child will be born with the condition: 1/900
If you’re the 1/900 couple, be glad you know- you’ve just averted a pretty bad disease. And there are still ways the two of you can get pregnant together safely. (If you met your partner at a family reunion, the math changes radically).
These tests are recommended by various medical societies so insurance companies will usually pay for them. However, they usually pay to test the woman first and if positive, then test the man. Since they’re genetic tests, the results are unlikely to change so if you think you want a kid a year or two from now, you can have them done today before you get busy.
Dr. Fickie is a board certified geneticist. He completed his fellowship in medical genetics at Harvard University and completed a Master of Arts in Medical Ethics and Law at the University of Manchester. He is an attending physician at Baystate Medical Center in the Division of Medical Genetics, and is on the faculty of Tufts University School of Medicine. His hobbies include going to the playground with his wife and daughter