Prenatal Carrier Screening for Genetic Conditions

After completing this article, readers should be able to: 1. Discuss the benefits and limitations of carrier screening. 2. Describe the recommendations for screening for hemoglobinopathies. 3. List the genetic disorders for which carrier screening is available for individuals of Ashkenazi Jewish ancestry. 4. Describe the recommendations for cystic fibrosis carrier screening. Carrier screening for hemoglobinopathies, Tay-Sachs and Canavan diseases, and more recently, cystic fibrosis has been incorporated into routine obstetric care. These genetic disorders are autosomal recessive, and when both members of a couple are carriers, there is a 25% risk of having an affected child in each pregnancy. Although many states routinely screen newborns for sickle cell disease and cystic fibrosis, recognition that a couple is at increased risk for having a child with one of these disorders permits a wider array of options, including antenatal diagnosis and termination of an affected fetus. In some cases, identification of an affected fetus allows a couple, their obstetrician, neonatologist, pediatrician, and pediatric specialists to prepare for the birth of an affected fetus. Screening completed prior to conception provides couples with additional reproductive options to consider, including donor gametes, preimplantation genetic diagnosis, and adoption if they choose to reduce their risk of having an affected child. As a result of the Human Genome Project and advances in technology, DNA-based tests can be used for carrier screening and prenatal diagnosis for many inherited conditions. In addition to screening for sickle cell disease, thalassemia, and Tay-Sachs disease, carrier screening now is available for cystic fibrosis, Canavan disease, and other disorders that are more common in individuals of Ashkenazi Jewish ancestry. Carrier screening recommendations for these genetic conditions is based on a person’s ethnicity. However, the importance of family history cannot be underestimated. The family history is used to determine whether an individual or couple is at increased …