Genetics and Carrier Screening
All couples where even one partner has Jewish ancestry should consider carrier screening for the Jewish genetic diseases prior to conception.
If both parents are carriers), there is a 1-in-4 chance for each pregnancy that the child will be affected by the disease.
In an autosomal recessive condition (such as most Jewish genetic diseases), persons who inherit only one mutated gene show no signs of disease, but persons who inherit two mutated genes will be affected by the disease.
If two carriers of the same disease(s) have children, there is a 1-in-4 (25%) chance with each pregnancy that their child will be affected with that disease, a 2-in-4 (50%) chance that the child will be a carrier, and a 1-in-4 (25%) chance that the child will neither be affected nor a carrier.
It is important to note that the 1-in-4 chance of having an affected child is for each pregnancy, regardless of the outcome of prior pregnancies.
What it Means to be a Carrier
Carriers are usually healthy individuals who are often unaware of their carrier status prior to screening, or until they have a child affected with the disease.
A carrier is an individual who does not develop the disease but can pass on the gene to his or her child. In the case of these Jewish genetic diseases, which are termed autosomal recessive one parent can pass on their carrier status, but both parents need to be carriers of the same disease to have an affected child.
In the case of Gaucher Disease Type 1, patients are occasionally diagnosed in the course of carrier screening.
Carrier couples who are identified early can be offered genetic counseling in order to help them understand their options for building a healthy family before they become pregnant. That is why the JGDC strongly recommends that anyone with even one Jewish grandparent consider genetic screening before starting a family.
How is Screening Done?
A blood sample is drawn and sent to a genetics laboratory for DNA analysis.
After several weeks, a report is available which shows whether or not the individual is a carrier for the diseases included in the carrier screening. The report should be carefully read by a knowledgeable doctor or trained genetic counselor.
For Tay-Sachs Disease, enzyme analysis in addition to DNA analysis is recommended. For Alpha- and Beta-Thalassemia, a complete blood count (CBC) is done first. If the CBC indicates impaired production of an important blood protein, DNA analysis is then conducted.
Where is Screening Done?
Screening can be requested through a doctor’s office, usually an OB/GYN, or medical genetics program where genetic counseling is available. If one or both partners test positive for carrier status, they should be referred for genetic counseling.
It is important to tell your doctor or genetic counselor that you have Jewish ancestry and that you are considering starting or adding to a family. Share your family’s geographic heritage and discuss any genetic conditions that run in your family.
If your family is of Mizrahi or Sephardic origin, you may want to go directly to a hospital-based genetic program with experience in these diseases. Visit our resources section for more information.
Who Should be Screened? In a Couple, Who is Screened first?
In a couple where both partners are of Jewish heritage, the usual practice is to screen the woman first, generally at her OB/GYN office. If she is found to be a carrier, her partner should be screened for the disease or diseases she carries
If only one partner is of Jewish heritage, that partner should be screened first. If he or she is found to be a carrier, the other partner can then be screened for the disease or diseases carried by the first partner.
If the couple is already pregnant, both partners should be screened at the same time.
In the case of a single woman wishing to become pregnant , or same-sex partners where donor egg or sperm is being used it should come from a donor who has been screened for Jewish genetic diseases.
When is the Best Time to be Screened?
Carrier screening prior to pregnancy is optimal. If both partners find that they are carriers of the same disease, they will have ample time to research the disease they carry, discuss their reproductive options with a genetic counselor and other advisors, and make an informed decisions about the best way for them to begin a family.
Screening can be done for a pregnant couple. It is important to note that if the couple discovers their carrier status once they are already pregnant, their only options, if the fetus is affected, are to continue or terminate the pregnancy.
If the woman is already pregnant, both partners should be screened at the same time. If they are both found to be carriers, this allows for earlier fetal testing and decision-making.
It is also important to note that fetal testing for Jewish genetic diseases is not possible unless the parents are already screened and their particular genetic mutations are identified.
A report is generated by the testing laboratory and must be read and interpreted by a doctor specializing in genetics or a genetic counselor.
A screening report is not a simple yes/no. It will tell the doctor or genetic counselor what the chances are that the patient is a carrier of a particular disease, but there is always a residual risk that the patient has an unidentified mutation and may still be a carrier.
Individuals should request a copy of their test results and keep it in a safe and easily accessible location. As new diseases are added to the panel, screening for additional diseases may be necessary with subsequent pregnancies.
Carrier Screening Recommendations Depend on Family Heritage
There are different genetic concerns for Jewish people of Ashkenazi background (Germany or Eastern Europe), Mizrahi (Iran/Persia, Middle East, Uzbekistan, Eastern Caucasus) and Sephardic (Mediterranean) background. (see Jewish Genetic Diseases)
Although every insurance plan is different, many cover testing for Jewish genetic diseases. Your doctor’s office, or a medical genetics program, can tell you whether your particular plan covers carrier screening. If screening is not covered, the JGDC may be able to recommend low-cost options or help provide special funding. Contact the JGDC for more information.
When it was first introduced, there were confidentiality concerns about genetic screening and a fear that data might be misused. This is longer be a concern.
In 2008 the Genetic Information Non-discrimination Act of 2008 (GINA) was signed into law. It’s a federal statute that protects American from being treated unfairly due to their genetic inheritance.
As of May 2009, health insurers may not deny or limit coverage or charge higher premiums based on a person’s genetic information. As of November 2009, employers may not use genetic information to make decisions about hiring, firing, promotion or job placement.
A genetic counselor is specially trained to interpret test results, interview and counsel couples, and often has an MS degree and a “Certified Genetic Counselor” or “CGC” designation. Most genetic counselors work at a hospital or medical school genetics program with medical geneticists; some larger OB/GYN practices have a genetic counselor in-house. The National Society of Genetic Counselors has an online listing of its members.
There are multiple options that enable carrier couples to build a healthy family. Each couple needs to make their own informed decision, based on the disease or diseases for which they are carriers and other personal considerations.
Genetic counselers can explain these options in depth. As you will see, it is best to know your carrier status before starting a family, so you can make informed decisions based on accurate genetic information.
• A carrier couple may choose to become pregnant and test the fetus early in the pregnancy.
In the case of a couple who would choose to get pregnant on their own, the couple should test the fetus early in pregnancy. This can be done by chorionic villus sampling (CVS) at 10-12 weeks, or an amniocentesis at 14- 16 weeks. In order to test the fetus, the parents’ carrier status must be known.
If the fetus is affected with the disease the couple carries they can choose to terminate the pregnancy or bring it to term. In the case where the couple chooses to give birth to an affected child having prior knowledge of the disease is extremely important. Information about the disease your child carries can help you to be aware of medical necessities and interventions that the child may require at birth.
• A carrier couple may choose in-vitro fertilization (IVF) with pre-implantation genetic diagnosis (PGD).
The egg is fertilized outside the body and embryos are tested at a very early stage for the disease carried by the parents. Only unaffected embryos are implanted in the womb.
• A carrier couple may choose to use egg or sperm from a non-carrier donor.
The donor should be screened for the Jewish genetic diseases.
• A carrier couple may choose to adopt.
• A carrier couple may choose not to have children.
• A carrier may choose not to marry another carrier of the same disease.
If you or your partner come from a family with Jewish ancestry and plan to become pregnant, it is important that you ask to be screened for the appropriate Jewish genetic diseases.
If you are already pregnant, it is important to discuss screening with your doctor as soon as possible.
Tell you doctor about:
• Your plans to become pregnant
• You and your partner’s family background, whether Ashkenazi, Mizrahi or Sephardic.
• Any family history of genetic diseases.
If you have been screened before, and your test results are available, bring them to your appointment.
If you don’t have a doctor or if your doctor doesn’t offer genetic screening and counseling, you should contact a hospital-based medical genetics program in your area. Click here for a national listing, or search for a genetic counselor in your area at NSGC.org.