Perinatologists in the Maternal-Fetal Medicine Clinic at Valley Medical Center have 2-3 years additional, specialized obstetrics/gynecology training focused on the assessment and management of high-risk pregnancies.
Prenatal Testing
Pregnancy can be an exciting and confusing time. Before choosing any prenatal tests, you should discuss this information with your provider and/or genetic counselor. By doing so, you will obtain the information you need to make the best decisions for you and your baby.
Diagnostic Tests
CVS: Chorionic villus sampling involves removing a small amount of tissue from the placenta between11-13 weeks. The doctor removes this tissue either by going through the mother’s abdomen with a thin needle, or through the vagina with a thin tube. UItrasound is used to help guide the doctor during the procedure
Amniocentesis: Amniocentesis involves removing a small amount of amniotic fluid (water that surrounds the baby). The doctor uses ultrasound to help guide a thin needle through the mother’s abdomen to get this fluid. This test is done any time after 15 ½ weeks.
Why Consider Prenatal Testing?
Most babies are born healthy, but all pregnant women have a 3-5% chance to have a baby with a birth defect or mental retardation. Many parents are concerned about these risks and prenatal testing can help them detect some of these problems. Your test results can reassure you that your baby is healthy, help you prepare for a baby with special needs or alert you if a serious problem is detected.
What Kinds of Tests are Available?
During your pregnancy, you can choose a prenatal and/ or diagnostic test. A prenatal screening shows the chance for certain conditions in pregnancy but cannot actually diagnose them. The conditions screened for include Down syndrome, Trisomy 18 and spina bifida.Information from screening tests is used to decide whether to have a diagnostic test such as amniocentesis. We offer several prenatal screening tests at our clinic. Most screening tests require a blood draw. Some also use a nuchatal translucency (NT) ultrasound to measure the fluid at the back of the baby’s neck. Screening tests do not increase the risk for miscarriage. Only one prenatal screening test is done during pregnancy. A prenatal diagnostic test is used to diagnose certain conditions such as Down syndrome during pregnancy. Diagnostic tests are offered to women who: have had a positive prenatal screening test, are over 35 years of age, have had a previous pregnancy or child with a chromosome condition, or who have a family or personal history of a genetic condition. Prenatal diagnostic tests involve a small risk of miscarriage. Chronic villus sampling (CVS) and amniocentesis are two diagnostic tests offered in our clinic.
One-Step Screening
First Trimester Only Screening
The first trimester only screen involves a single blood draw and NT ultrasound between 11-13 weeks. The results will estimate the chance for Down syndrome and Trisomy 18 in the baby. The screen can detect about 83% of pregnancies with Down syndrome. About 5% of patients will get a screen positive result even though the baby does not have Down syndrome. If your screen is positive, diagnostic options of CVS or amniocentesis are available to you.
Quad Screen (Second Trimester Only)
The quad screen involves a single blood draw between 15 and 22 weeks. The results estimate the chance for Down syndrome, Trisomy 18 and spina bifida in the baby. The screen can detect about 75-80% of pregnancies with Down syndrome. About 5% of patients will get a screen positive even though the baby does not have Down syndrome. If your screen is positive, the option of amniocentesis is available to you.
Two-Step Screening
Sequential Screen
(first +/- second trimesters)
The Sequential Screen is usually done in two parts. Part one is similar to the first trimester only screen, involving a blood draw and NT ultrasound. If results from part one reveal a high chance for Down syndrome, you will be notified in a few days.You provider or genetic counselor will offer the options of CVS or amniocentesis. If the result from part one is not a high risk, you will not get results yet, but instead have a second blood draw between 15 and 22 weeks. Results from the two parts are combined to give a more accurate risk assessment for Down syndrome, Trisomy 18 and spina bifida. If part two is positive, you have the option of amniocentesis for diagnostic testing. This two-step screen can detect about 92% of pregnancies with Down syndrome. About 3-4% of patients will get a screen positive result even though the baby does not have Down syndrome.
What if My Prenatal Screen is Positive?
REMEMBER: A screening test only estimates the chance for certain problems. A positive screen does not mean there is definitely a problem with the baby. If your screening test is positive, you can talk to a genetic counselor about the results. A genetic counselor can help you understand the results and work with you to decide if you should have a prenatal diagnostic test.
Frequently Asked Questions
Are these procedure safe?
The maternal fetal medicine doctors are specialists who have many years of experience with high-risk pregnancies and special procedures. The most recent studies suggest that the risk for complications and miscarriage after CVS or amniocentesis is very low with experienced providers such as ours.
Will my activities be restricted following my procedure?
After your procedure, you can do most normal activities, including walking and driving. For the next 24 hours, you should not lift anything heavier than 10 pounds; participate in strenuous activity or exercise; or have sexual intercourse.
When do I receive results?
Results are usually ready in about 2 weeks. A genetic counselor will call you to discuss the results as soon as they are available. Your doctor/midwife will also receive a letter with your results.
Will a normal test guarantee a normal baby?
No. Both CVS and amniocentesis will identify chromosome conditions such as Down syndrome. These tests do not detect other kinds of problems such as cerebral palsy, autism, heart defects and many forms of mental retardation.
How can I learn more about my options?
You can learn more about your options by talking to your doctor/midwife or by calling our schedulers at the Maternal Fetal Medicine Clinic to set up an appointment with a genetic counselor. They are available Monday through Friday.