Genetics Testing
Details of a Genetics Testing Consultation
In the last post, I mentioned that I often talk with my patients about their options in genetics testing during the first prenatal appointment, but it actually goes much further. The genetics testing consultation is a separate appointment altogether.
If you were my patient, here’s what we’d discuss in this special consultation:
- A detailed health history of both mom and dad to find out if you are at risk of having a baby with a disorder.
- An overview of the tests available to you, the risks of each, and the reasons you may or may not want to proceed with each test.
- Options available to you should you discover that your baby may have a genetics disorder.
Understanding Genetics Disorders
You may remember that genetics are the traits passed from both parents to the child. The mother’s egg and the father’s sperm each have 23 chromosomes, which pair up within each cell of the fetus. Each of the 46 chromosomes contains a number of paired genes, some recessive and some dominant, which define a number of traits. These traits range from the color of the baby’s eyes to blood type.
A genetics disorder can result from a missing or damaged chromosome or gene or when inherited from a parent. Disorders could include Huntington’s Disease, Tay-Sachs disease, cystic fibrosis, hemophilia, Down syndrome, and others.
Types of Tests Available to You
Carrier test – A blood or saliva test completed at any time to determine if either parent is a carrier of a genetic defect.
Chorionic villus sampling (CVS) – Between 10-12 weeks, a sample of cells from the placenta is tested to find chromosomal problems.
Nuchal translucency screening – Between 10 and 14 weeks of pregnancy, this special ultrasound and blood test look for signs of Down syndrome, trisomy 18, and heart defects.
Maternal serum screening – Between 15 and 20 weeks of pregnancy, a blood test that measures certain substances to determine if the there is an increased risk of a neural tube defect, abdominal wall defect, Down syndrome, or trisonomy 18.
Amniocentesis – Between 15-20 weeks, a needle can be used to draw amniotic fluid and cells from the sac around the fetus to check for chromosomal problems.
Detailed ultrasound exam – If a screening test shows there is an increased risk, a detailed ultrasound will help to explain the screening. Test can be completed anytime after 18 weeks of pregnancy.
Fetal blood sampling/cordocentesis – Blood is taken from the umbilical cord when the results of an amniocentesis or CVS are not clear.
What Happens When You Decide To Do Genetics Testing
Ultimately, you get to choose what, if any, genetics testing you have done during your pregnancy. Depending on what the doctor finds, you may need additional tests, the doctor may want to monitor the baby more closely, you may need to deliver sooner than expected, or, nothing will be done at all, because you and your baby’s health looks fine.
Other Special Testing During Pregnancy
Not all prenatal testing looks for genetics disorders. You doctor may want you to complete any number of special tests to look for potential problems (tests include fetal movement counts, ultrasound, Doppler ultrasound of the umbilical or other artery, nonstress test, biophysical profile, and contraction stress test).
As published by the American Congress of Obstetrics and Gynecology (ACOG), most obstetricians will request frequent tests if you have any of the following:
- Blood disorders
- Thyroid disease
- Heart disease
- Lupus
- Kidney disease
- Diabetes
- High blood pressure
To read more about genetics and special prenatal testing, visit our library of resources that contains a pamphlets published by ACOG. You may also subscribe to our RSS feed to get our blog updates directly to your feed.
