Genetic Carrier Screening

Published: 12/15/2015

Arizona Center for Fertility Studies recommends carrier screening to everyone planning for pregnancy. Carrier screening is a genetic panel that can be performed on potential parents before pregnancy to see if they carry genetic variants, or mutations, that could affect the health of their future children.

Carrier screening mainly detects three types of illnesses:

  • mild conditions that can affect a woman’s ability to become pregnant or lead to other risks during pregnancy (e.g., MTHFR or Factor V Leiden deficiency)
  • autosomal recessive traits that will only cause problems if the partner is also a carrier of a mutation for the same genetic disorder (e.g., cystic fibrosis and spinal muscular atrophy)
  • X-linked disorders (e.g., Fragile-X) which typically affect males more than females because of the presence of a single X chromosome

Having this information ahead of time prepares patients. An abnormal carrier screen may lead to early testing of the fetus during pregnancy or preventative strategies like IVF with preimplantation genetic testing.

What Is a Recessive Disease?

We have two copies of each gene, one inherited from each parent. Autosomal recessive diseases are only expressed when an individual has two abnormal variants affecting the same gene. Many people are silent, healthy carriers for recessive genetic mutations because one normal copy of a gene is usually enough to keep us healthy. However, if each future parent carries an abnormal variant of the same gene, their children will have a one-in-four chance of inheriting two abnormal copies and can be severely affected by a genetic disease.

What Diseases Are Tested?

The genetic carrier-screening screens for recessive genetic disorders like Cystic Fibrosis, SMA (spinal muscular atrophy), Fragile-X syndrome, Tay-Sachs, Sickle Cell Disease, and many others. Such conditions can significantly affect your child's normal development and health. Treatment may be available for some disorders, but that is not the case for every disease.

Family History and Genetic Disease

Even if you don't have a family history of any of the diseases included in the genetic carrier-screening test, you may still be a carrier. In fact, the majority of recessive disorders occur in families without a history of genetic disease, and most people do not realize they are carriers until they have a child born with a genetic condition.

What if I Am a Carrier?

While carriers are typically healthy individuals, they may occasionally have mild symptoms. However, it is only when both parents are carriers of the same genetic disease that they are at risk of having a child affected with that disease. The likelihood that both parents are carriers for the same mutation is around 1%. Partner testing is strongly recommended if you are a carrier for a disorder of severe consequence.

What if We Are Both Carriers?

If you and your partner are both found to be carriers of the same genetic disease, your child will usually have a one-in-four chance of having the condition. If this occurs, ACFS will discuss with both of you all of the available medical options.

Risk-Reducing, Not Risk-Eliminating

Carrier screening does not and cannot screen for all possible genetic variants that may be associated with disease. Thus, carrier screening drastically reduces (but does not eliminate) the chance for recessive genetic disease. Moreover, the test is not intended to diagnose diseases like Down Syndrome, which is a chromosome abnormality. Chromosome abnormalities usually occur by chance, but the risk of fetal chromosome abnormalities increases with age. The risk of chromosomally abnormal conception can be reduced with preimplantation genetic testing for aneuploidy screening (PGT-A).