Screening For Fetal Abnormalities
First Trimester Screening
First trimester screening with nuchal translucency ultrasound and the maternal serum quad screen are two available tests to estimate your chance of having a baby with certain chromosome abnormalities. One of these tests or the other is performed, not both. Nuchal translucency is an ultrasound that looks at the fluid at the back of the baby's neck. The serum quad screens are tests done on the mom's blood.
First trimester screening can be done in the first trimester of pregnancy, between 11 weeks and 13 weeks, 6 days.
Nuchal Translucency Ultrasound
This includes the nuchal translucency ultrasound and some blood tests on mom. First trimester screening estimates your risk of having a baby with Down Syndrome, Trisomy 18, and Trisomy 13, but it does not diagnose chromosome conditions.
Maternal Serum Quad Screening
Another option for estimating your risk for certain chromosome conditions is maternal serum quad screening which can be performed at 15 or more weeks in pregnancy. Maternal serum quad screening estimates the chances of having a baby with Down syndrome, Trisomy 18, and spinal bifida. If the screening test results indicate an increased risk of having a baby with a chromosome condition, diagnostic testing can be elected.
Diagnostic Testing Options
Diagnostic testing options include chorionic villus sampling (CVS) that can be done between 10-14 weeks in pregnancy or amniocentesis, which is done at 16+ weeks during pregnancy. You can review the screening options and diagnostic testing options with your doctor, and if you would like more information, your doctor can refer you to see a genetic counselor.
Cystic Fibrosis Testing
Cystic fibrosis is a life-long illness that is usually diagnosed in the first few years of life. The disorder causes problems with digestion and breathing. Cystic fibrosis does not affect intelligence or appearance.
The purpose of CF testing is to see if a couple is at increased risk for giving birth to a child who will have CF. Cystic fibrosis carrier testing is a laboratory test done on a sample of blood. If CF testing shows both parents are carriers, you might then choose to see a provider for genetic counseling to obtain more information and help you decide if you want to test the baby for CF.
This testing on the baby could be done around the 10th week of pregnancy using CVS (chorionic villus sampling). Or it could be done around the 16th week of pregnancy using amniocentesis. For more information talk to your physician or contact the Cystic Fibrosis Foundation at 800-344-4823 or visit their Website.
Second Trimester Testing
The following blood tests are usually done during this time. Don't hesitate to talk with your doctor if you have questions on any test.
Maternal Serum Alpha-Fetoprotein (MS-AFP)
A blood sample obtained between the 15th and the 18th weeks of pregnancy is an optional test used to detect neural tube defects such as spinal cord abnormalities or an anencephaly (absence of brain). Any positive results are followed by further testing (for example, another MS-AFP, ultrasound, amniocentesis, or genetic counseling).
Glucose Screening
The glucose test is used to rule out diabetes and is performed between the 24th and 28th weeks of pregnancy. One hour after drinking a glucose solution, a blood sample is drawn. If an elevated blood sugar level is reported, a glucose tolerance test may be requested by your doctor. This test requires hourly blood samples drawn after drinking the glucose solution. During routine prenatal office visits, your urine will be checked for signs of diabetes.
Third Trimester Testing
Group B Strep Testing
Group B strep is a common bacteria and is almost always harmless in adults. In rare cases, a woman who has group B strep can infect her baby during delivery. This can cause serious illness in the newborn. For this reason, your doctor may obtain a culture from you between 34-36 weeks of your pregnancy. A cotton swab is used to collect cell samples from your vagina and anus. The samples are sent to the lab for testing which takes at least two days. If you have a positive Group B strep culture, you will be given intravenous antibiotics during labor to protect your baby from possible infection.
Ultrasound
This is an optional exam that may be requested by your doctor at any time during your pregnancy. During the test, the fetus can be viewed on a monitor screen. An ultrasound may be used for the following reasons:
- Assist in determining due date
- Check for bleeding
- Detect multiple gestation (twins, triplets, etc.)
- Check positioning of the placenta, baby and certain body organs and structures
- Determine baby's well-being
- Check the level of amniotic fluid. In some high risk pregnancies, the amniotic fluid may decrease during late pregnancy and jeopardize the baby's health.
Most insurance plans do not pay for routine ultrasound, but will pay if there is a medical reason to have an ultrasound.
Non-stress Testing
This test uses an external fetal monitor to check fetal heart rate in relation to the baby's movement and can take 30 minutes or more. It is not performed routinely; only when pregnancy continues after the due date or when there is concern about your baby's well-being.
Amniocentesis or Chorionic Villi Sampling
Amniocentesis and chorionic villi sampling are not routine and are reserved for specific situations. Your doctor will discuss these exams with you if you are a candidate for them.