In the third episode of the Prenatal Genetics series, Dr. Goldwaser and Dr. Fox discuss carrier screening. Carrier screening involves checking two potential parents’ DNA to see whether they have a genetic condition that could be passed on to a fetus, and is usually performed before a pregnancy. Dr. Goldwaser explains that most people are carriers for something, and why in most cases, this isn’t a cause for concern. They also discuss why parents may pursue genetic carrier screening and what to do if they are both carriers for a mutation.
“We’re All Mutated: Carrier Screening” – with Dr. Tamar Goldwaser
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In the third episode of the miniseries on prenatal genetics, Dr. Tamar Goldwaser returns to talk about carrier screening. Carrier screening is a test to see whether parents have genetic conditions present in their DNA that could be passed on to a fetus.
Dr. Goldwaser explains that most people are carriers for some condition, meaning that one of their two copies of a gene is in some way defective. This can occur even if the individual is healthy, because their other copy of that gene is working fine. She explains that we each have two copies of each gene: one from our father and one from our mother. Mutations in genes can exist in families for many generations without anyone being affected, because they are recessive. Conditions and complications only arise when both partners are carriers, causing a chance that their child is affected. For most genetic conditions, individuals only have the disease if both copies of their gene are mutated.
Current carrier screening can check for over 300 conditions, so there is a very high likelihood that every person will be found to be a carrier for something. Couple can have carrier screening to see if their child is at greater risk for a condition such as cystic fibrosis or Tay-Sachs disease. If both parents are found to be carriers, there is a 1 in 4 chance that their child will be affected. Dr. Goldwaser explains that both parents are found to be carriers for the same condition in only about 1% of cases.
Dr. Goldwaser also explains why couples would decide to have genetic carrier screening. In the past, patients were generally only advised to pursue carrier screening if they fell into certain ethnic groups. However, with a wider range of conditions that can be tested for, genetic carrier screening is becoming more likely. In what is called “cascade testing,” patients may choose to have carrier screening if one of their siblings or a close family member has previously found they are a carrier for a disease. Genetic carrier testing can also be helpful for parents who want to plan ahead for immediate medical care for a child born with a condition. Dr. Goldwaser notes that it’s often easier to arrange medical care and educate yourself before the baby is born rather than while caring for a newborn.
Finally, Dr. Goldwaser explains that testing is becoming more widespread as it is more accessible and a wider range of conditions can be tested for. However, she also notes that in some cases, this can cause complications due to a shortage of genetic counselors in some areas.