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Genetic Carrier Screening

At the time of your appointment, we ask you some questions about your family history and ethnic background. There are several genetic conditions that are more common in specific ethnic groups. The information below briefly reviews some general information about testing for these conditions. If you have questions about this information, please address them with the doctor during your scheduled appointment.

What are genes?

Genes are made up of a chemical called DNA and are the codes or instructions that tell the body how to grow and develop. These genes are arranged on strings of information called chromosomes. We have two copies of each chromosome, one that is inherited from our mother and one that is inherited from our father; as a result, we have one copy of each gene.

What are recessive diseases?

Many conditions are now known to be caused by changes, or mutations, in genes. Some genetic conditions, known as recessive conditions, are caused when a change or mutation is present on both genes of a pair. This means that both the mother and father must pass on the same changed gene in order for a child to have a recessive condition.

What is a carrier?

A carrier is a person who has a change in only one gene of a pair and the other gene of the pair is working normally. A carrier is sometimes said to have the disease trait but has no physical symptoms of the disease. In many families, a recessive gene change or trait can be passed on through generations without ever being known. A recessive disease can only occur if a person who is a carrier has a baby with another person who is also a carrier. Such a couple would have a 1 in 4 (25 percent) chance, in each pregnancy, of having a baby with that recessive disease.

Who should be screened?

DNA tests are available to help a couple determine if they are carriers of the same recessive disease trait and are at risk for having children with that recessive condition. Some diseases occur more often in certain ethnic groups. At the Johns Hopkins Fertility Center, we offer expanded carrier screening that screens for more than 170 genetic conditions that are inherited in a recessive fashion. The tested conditions are either life-threatening or could result in a child with serious, life-long health problems. Although it is not mandatory, we highly recommend expanded carrier screening for all our patients.  

What can be done if my partner and I are both carriers for the same condition?

If both parents are determined to be carriers of mutations for the same disease, the Johns Hopkins Fertility Center offers in vitro fertilization (IVF) with preimplantation genetic diagnosis (PGD), which can screen your embryos and help you to select the embryos that are not affected by the genetic disorder before that embryo is transferred into the mother’s uterus.

Is there prenatal testing?

If both parents are determined to be carriers of mutations for the same disease and elect not to pursue IVF with PGD, a prenatal test is available to determine if the baby is affected with the recessive disease. This testing may be available as early as 1018 weeks gestation of pregnancy.

How can I have carrier testing?

If you are interested in learning more about the genetic carrier screening, please talk to your fertility doctor at your new patient appointment.