What Everyone Should Know About Ethnic-Based Genetic Screening Before Pregnancy
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Many populations of the world have specific genetic conditions that are prevalent within their ethnic group. Consequently, numerous medical organizations have recommended that genetic screening for these conditions should be offered when women are either planning for, or are currently pregnant. We are all carriers of genetic conditions: generally this is of little concern, as it is highly unlikely that we would have children with a partner who is a carrier for the same condition.
The genetic conditions listed in the table below are recessive. A recessive gene mutation is “carried” by someone who is unaffected by the disease, and thus unaware of their carrier status. Men and women have equal potential to be carriers for recessive conditions. Even if someone is a carrier, we would not expect to see a family history of the disease. If there is a family history, the likelihood of being a carrier of that condition is generally greater than in the general population. Being a carrier for a genetic condition typically has no impact on the carrier’s health and development. However, if a carrier has a child with another carrier of the same genetic disease, the chance that the child will be affected with the disease is 1 in 4 (25%).
If only one partner is a carrier, and the other tests negative, then the risk of an affected child is low, but not zero (a result of the limited ability to test for all defects that would make one a carrier; see table). These genetic screening tests are typically performed on a blood sample.
Below is a table listing the minimum number of tests for various ethnic groups recommended by the physicians at Pacific Fertility Center prior to starting assisted reproduction treatment. Additional genetic tests may be considered after a discussion with your physician.
If you know that both you and your partner are carriers of the same genetic defect, you may be able to have embryos created in an IVF cycle and tested for their status. Preimplantation genetic diagnosis (PGD) is a technology that allows embryos to be tested for specific disease causing mutations. PGD can identify unaffected embryos for transfer back to the uterus or freezing.
—Guest Contributor – Certified Genetic Counselor Lauri Black, M.S., C.G.C
| Ancestral Population | Genetic Desease | Carrier Frequency | Detection Rate* |
| All | cystic fibrosis | Approximately 4% in people of European (and Ashkenazi Jewish) ancestry and less common in other populations | Approximately 88% for Europeans, 94% for Ashkenazi Jewish ancestry, less accurate for others |
| Ashkenazi (Eastern European) Jewish ancestry | cystic fibrosis, Tay Sachs, Canavan, familial dysautonomia | Approximately 3% for Tay Sachs, 2% for Canavan and 3% for familial dysautonomia | Approximately 94-99%, (depending on the condition tested) |
| African/African-American, Chinese, Southeast Asian, or Mediterranean ancestry | Hemoglobinopathies, such as sickle cell anemia and thalassemia | Approximately 10% of African-Americans are sickle cell carriers; 5-6% of Asians and 12% of some Mediterranean populations are thalassemia carriers. | Variable depending on method, but very high (in the 90 percentiles) |
*See lab specific accuracies on test result
Tags: Fertility Testing, IVF - In Vitro Fertilization, PGD - Preimplantation Genetic Diagnosis
