Special Diagnostic Tests During Your Second Trimester of Pregnancy



Depending on your age and certain risk factors, your health care provider may recommend special tests such as an ultrasound scan, AFP (alpha-fetoprotein) screen, amniocentesis, and a diabetes screen. Make sure that you fully understand the benefits and risks of each test (use these questions about prenatal tests as your guide) before you give your consent.

An ultrasound scan uses sound waves to create a picture (called a sonogram) of the fetus. Ultrasound scans can be used anytime after five weeks of pregnancy. Your doctor or midwife should have a medical reason for performing one. Although no known side effects have been identified, no one really knows what the long-range effects are. Ultrasound scans are done for many reasons, including determining whether you are going to have more than one baby; more accurately estimating your due date; and seeing how well the baby is growing.

The alpha-fetoprotein (AFP) screen is a blood test usually offered between 15 and 18 weeks of pregnancy to screen for certain birth defects like spina bifida or Down Syndrome. The AFP only indicates increased risk for some birth defects; it does not establish that a birth defect exists. Therefore, if an AFP shows an abnormal result, further testing (usually extensive ultrasound and/or amniocentesis) is required.

Amniocentesis is usually performed between 14 and 18 weeks. The test involves inserting a long, thin needle through your belly into the uterus (using ultrasound as a guide) to withdraw a few teaspoons of amniotic fluid. It is used to determine whether the fetus has a genetic defect. The results, which are very accurate, are available in about two weeks. Amniocentesis carries a small risk of infection, hemorrhage (bleeding that is difficult to stop), leaking of amniotic fluid, and/or miscarriage.

Diabetes screening may be conducted between 24 and 28 weeks. It is a simple test called a glucose tolerance test and involves drinking a liquid containing glucose (sugar) and taking a blood sample one hour (and sometimes at one-, two-, and three-hour intervals) after. Some pregnant women develop a temporary condition known as gestational diabetes. This means they have a higher than normal sugar level in their blood and need special monitoring.

On your way
Your partner, health care providers, friends, and family can all provide support as you continue your journey into the third trimester of pregnancy. But don't forget to listen to yourself and trust your feelings.

Continue to "The Third Trimester" journey to parenthood

Most recent page update: 9/9/2010


© 2014 National Partnership for Women & Families. All rights reserved.

Founded in 1918, Childbirth Connection has joined forces with and become a core program of the National Partnership for Women & Families. Together, these two women's health powerhouses are transforming maternity care in the United States.
News and Features
Special Announcement

Childbirth Connection has joined forces with and become a core program of the National Partnership for Women & Families.
Read more


Our History

This interactive timeline highlights our trailblazing work since 1918.
Launch timeline


Our Vision

We want all women and babies receive the best possible maternity care.
Play video


Featured Resource

Check out our resource, "New Cesarean Prevention Recommendations from Obstetric Leaders:What Pregnant Women Need to Know"
Read more


Get Involved

Read our 2020 Vision, Blueprint for Action, blog and more
Sign up for email updates
Find us on Facebook
Follow us on Twitter
Support us