More than 95 percent of pregnancies end with a normal, healthy outcome. However, every pregnancy carries some chance of a fetus having a birth defect or genetic condition. Some, but not all of these, can be detected before birth through various types of genetic screening or testing. It is important for parents to remember that no test can guarantee the birth of a healthy baby.
Screening tests are helpful ways to determine if a pregnancy is at higher risk for certain conditions. However, it is important for parents to remember that screening tests cannot determine whether a fetus is affected with a condition, only that a pregnancy may be at higher risk.
Diagnostic testing, on the other hand, can determine if a fetus has a specific condition. Diagnostic genetic testing options include CVS and amniocentesis.
The risk for disorders, such as Down syndrome, are more frequent as mothers get older; however, there is some risk involved in every pregnancy.
Performed between 11 and 13.6 weeks, first trimester screening combines an ultrasound and a blood test to calculate the chance for chromosome-related conditions.
A second ultrasound is recommended at 18–20 weeks to help identify other problems, such as heart defects. Some doctors recommend a second blood test (referred to as a sequential screen or AFP screen) at approximately 16–18 weeks to further evaluate the risk for chromosome abnormalities and other problems.
If an increased risk for a chromosome abnormality is revealed, diagnostic testing will be offered.
Fetal DNA can be examined in a maternal blood sample after 10 weeks gestation. This test measures the amount of DNA from specific chromosomes and can detect chromosome-related problems. The test also accurately predicts the fetus's gender.
Sometimes perfectly normal parents can have a fetus with genetic disorders. Cystic fibrosis, sickle cell anemia and Tay-Sachs disease can occur when both parents carry the same abnormal gene, but do not have the disease themselves. These parents are carriers of recessive genetic diseases that can be inherited by their fetus.
Some genetic disorders occur more frequently within certain ethnic groups, and carrier screening is available for many of these conditions. Our providers will meet with you and recommend which tests you should consider based on ethnicity and other factors.
Optional expanded carrier screenings can test for a wide range of recessive genetic disorders.
If a family member has a genetic condition, you may have reason to be concerned about passing the same condition on to your fetus. Preconception and prenatal testing are available for many hereditary disorders. Contact us as early as possible so that we may determine what type of genetic testing is appropriate for you.