Many would-be or expectant parents face choices based on genetic considerations, especially if either parent has an inherited disorder or if a previous child or close blood relative does. They should talk to a genetic counselor about the appropriate options for screening and testing. The counselor will discuss the benefits, risks, and limitations of tests such as the following:
- Carrier tests show if parents have a gene for an inherited disorder. For instance, cystic fibrosis screening is recommended for all women considering pregnancy. Other tests may be recommended based on ethnicity. African-Americans are most likely to carry the gene for sickle-cell disease, for example, and Ashkenazi Jews as well as certain groups of French Canadians may carry genes for Tay-Sachs disease.
- After conception, diagnostic tests such as amniocentesis (analysis of amniotic fluid) or chorionic villus sampling of the placenta can determine whether a fetus has Down syndrome or other genetic disorders. Such testing is recommended for all women 35 or older, since they are at increased risk for having a child with a chromosomal disorder; or if either parent is known to carry a genetic mutation.
- Non-invasive prenatal testing, which analyzes cell-free fetal DNA circulating in maternal blood, is a newer option in prenatal screening for Down syndrome and a few other chromosomal abnormalities.
- Preimplantation genetic diagnosis (PGD), also called preimplantation genetic testing (PGT), is used in conjunction with in vitro fertilization (IVF) to allow doctors to identify, and not use, embryos that carry genetic mutations.
Genetic testing before and during pregnancy allows parents to prepare for possible problems and consider their options, such as adoption, donor egg or sperm, IVF with PGD/PGT, and termination of pregnancy.