There are several genetic tests available to you and your partner during your pregnancy. These optional, non-invasive tests help screen for genetic abnormalities that may affect your baby. What follows is a brief description of the tests available; we will discuss the options in detail at one of your first prenatal appointments. Please call the office at any time if you have additional questions regarding what testing is right for your family.
Carrier testing is screening for genetically recessive disorders that a parent may carry as part of his or her DNA. With a recessive disorder, both parents must carry the abnormal gene in order for a child to be at risk of being affected with the disease (approximately a 1 in 4 chance). We start with screening for the mother, and follow up with paternal testing if necessary. If both parents carry the same abnormal gene, we will refer you to genetic counseling to discuss how this may affect your pregnancy or child after delivery. Positive carrier screening does NOT automatically mean your baby has the disorder. These are screening tests only and assess risk, they do not diagnose disease.
They do not need to be repeated in future pregnancies as the results will not change (unless scientific advances have allowed for additional screening tests), and can even be done prior to conception. We recommend verifying insurance coverage before having the tests completed to make sure you are comfortable with the cost that may be involved.
Chromosome Abnormality Screening
This category of genetic testing refers to screening for abnormalities in fetal DNA, which result from abnormal cell division in early pregnancy. Disorders that fall under this category of screening include Down syndrome (Trisomy 21), Edwards syndrome (Trisomy 18), Patau syndrome (Trisomy 13), among others. Screening for these disorders in pregnancy are all risk assessments and do not diagnose a disease – if a couple desires a firm diagnosis, more invasive testing such as amniocentesis must be performed. Risk of having a baby affected with these disorders increases with maternal age, especially for those over 35 years old. Testing needs to be repeated each pregnancy, as the screening risk changes (different baby, different DNA).
The screening options for these disorders have evolved with advancing medical technology. We now recommend fetal free DNA testing, which requires a maternal blood draw after 10 weeks in pregnancy. This testing analyzes fetal DNA that can be found in a mother’s bloodstream, and has both a high detection and low false positive rate. These tests can also detect fetal sex, if you would like to know that information at the time of screening.
These companies have cost estimators on their websites and work with insurance companies for coverage. We do recommend establishing what your cost will be before having the testing drawn. If you find the cost to be prohibitive, there are other testing options that still provide screening and may be more affordable for you. These alternate tests typically involve a first trimester ultrasound and multiple blood draws. Please call the office or ask at an appointment for more details.
- Down syndrome — http://www.ndss.org/;
- Edwards syndrome — www.trisomy18.org;
- Patau syndrome — https://ghr.nlm.nih.gov/condition/trisomy-13#genes
During the second trimester of your pregnancy, at approximately 16 weeks, we recommend testing for Alpha-fetaprotein (AFP). This protein is a marker for fetal neural tube defects, such as spina bifida or anencephaly. If it is elevated, you have an increased risk of carrying a baby with one of these conditions. AFP elevation can also be a marker for possible placental problems in your pregnancy: this is another good reason to have the test done so that your provider can have the most information possible to help you have a healthy pregnancy. Like the other genetic testing, this is a risk assessment, and a positive result will require follow up for a diagnosis. This needs to be conducted every pregnancy as it reflects risks to the baby you are carrying at the time. You can confirm before the test is drawn, but most insurances cover this screening.