Screenings, Tests and Procedures
Genetic Screening and Tests
Starting in the early stages of your pregnancy, you have the option to screen and test for certain birth defects in your baby, such as:
- Down syndrome (trisomy 21)
- Trisomy 13
- Trisomy 18
- Neural tube defects
Decisions about genetic screening, prenatal testing and other options are very personal ones. Any additional questions can be directed to your provider, care team, genetic counselor or maternal fetal medicine team.
The first trimester screen: 11 – 13 weeks. This is a simple blood sample obtained by a finger stick combined with an ultrasound to estimate the risk of Down syndrome, trisomy 18, and trisomy 13.
Quad or Tetra screen: 15 – 20 weeks. The second trimester screen (Quad or Tetra screen) uses a blood draw to estimate the risk of Down syndrome and trisomy 18. This test is usually offered to women who have not had a first trimester screen.
MSAFP: 15 – 20 weeks. Maternal Serum Alpha Fetoprotein is a blood draw to screen for open neural tube defects such as spina bifida and other rarer conditions.
Noninvasive prenatal screening (NIPS): After 10 weeks. NIPS is a blood test that screens for chromosomal disorders such as Down syndrome, Trisomy 18, Trisomy 21 and sex chromosome abnormalities. This test can also determine the sex of your baby. This screen is recommended for mothers at increased risk for having a baby with birth defects, such as those of advanced maternal age, have history of chromosomal abnormalities, or previous abnormal screening results.
For patients identified for increased risk of having a child with birth defects, diagnostic tests are also available. These tests provide definitive information about birth defects as opposed to other screenings, which only identify the risk factors. However, diagnostic testing does carry a small risk of miscarriage. You should discuss the risks and benefits with your care provider. Some of the most common diagnostic tests include:
Amniocentesis: 15 – 20 weeks. In this procedure, a small amount of amniotic fluid is taken from the sac surrounding the baby and tested for conditions such as chromosomal abnormalities or neural tube defects.
Chorionic villus sampling (CVS): 10 – 12.5 weeks. In chorionic villus sampling (CVS), a small sample of cells is taken from the placenta and tested for conditions such as chromosomal abnormalities and cystic fibrosis.
Anatomy ultrasound: 19 – 21 weeks. The anatomy ultrasound provides a detailed look at your baby’s anatomy, taking measurements of all of his body parts and internal organs. This scan will help determine if your baby is growing and developing normally, and you can usually find out the sex of your baby at this time if you choose to do so.
1-hour glucose tolerance test: 24 – 28 weeks. (or sooner if you have a history of gestational diabetes or other risk factors). This test is used to screen for gestational diabetes. During the glucose tolerance test, you will drink a sugary drink containing 50 grams of glucose. After one hour you will have your blood drawn.
If your results are:
Under 135 mg/dL: You do not have gestational diabetes
135 – 199 mg/dL: Further testing is needed; your provider will order a three-hour test
200 mg/dL or greater: Diagnosed with gestational diabetes without further testing
3-hour glucose tolerance test: Unlike the one-hour, the three-hour glucose tolerance test is a fasting test, so you should not eat or drink anything for at least eight hours before your test. First thing in the morning before you eat breakfast is an ideal time for the test.
When you arrive at the lab, you will have blood drawn for your fasting blood glucose test. You will then drink a glucose drink containing 100 grams of glucose. You have your blood drawn again at the 1-, 2- and 3-hour marks. If two or more of your numbers are out of the normal range, you are diagnosed with gestational diabetes. You will need to monitor and control your blood glucose levels during the remainder of your pregnancy, through diet and exercise and/or medication.
Group B strep test: 35 – 36 weeks. Group B streptococcus (GBS) is a common type of bacteria that can live in the body, and may affect three out of every 10 women. It is generally harmless to adults, however it can be dangerous to your baby if passed to him or her during delivery. During this test, your provider will do a vaginal and rectal swab to test for GBS. If you are GBS positive, you will be administered IV antibiotics during labor in order to prevent infecting your baby with GBS.
Non-stress test: Your provider may order a non-stress test to measure the baby’s heart rate in response to fetal movement. A non-stress test may be performed if you are overdue, have been feeling the baby move less than usual, or have other complications or conditions that make you high-risk. During the test, two belts will be placed on your abdomen – one that measures the baby’s heart rate and one to measure contractions. Your provider will watch to see if the baby’s heart rate increases when he is active. The test should take about 20 minutes and is completely safe for both you and your baby.
Tdap: 27 – 36 weeks. The Tdap vaccine provides protection against tetanus, diphtheria, and pertussis. It is recommended that pregnant women receive this shot in the third trimester of every pregnancy. This ensures your own protection from these diseases, as well as passing protection on to your baby in utero.
It is also highly recommended that your partner receives a Tdap vaccine, as well as any other family members who will be in frequent contact with your baby after he or she is born.
COVID-19 Vaccine: The CDC now recommends all women who are pregnant or considering pregnancy get vaccinated for COVID-19. CDC recommendations align with those from professional medical organizations serving people who are pregnant, including the American College of Obstetricians and Gynecologists (ACOG), the Society for Maternal Fetal Medicine and the American Society for Reproductive Medicine (ASRM).
Flu shot: It is recommended that all pregnant women receive a flu vaccination before flu season. Contracting the flu while pregnant can be dangerous to both you and your baby. Since your baby cannot receive a flu vaccine for the first six months of his or her life, it is also recommended that anyone who will be in close contact with the baby receives a flu shot (including partners, other children, and close family members).
Rh immune globulin injection: After week 28. If you have an Rh negative blood type (as determined during your 1st trimester blood panel) you may need an Rh immune globulin injection after week 28 to prevent Rh compatibility issues with future pregnancies.