Second Trimester: Prenatal Labs


Second Serum Integrated Screen: If your first trimester test came back positive, you will be given the option to take a second serum integrated screen test. A second blood sample is taken to measure the levels of four markers:

  • Alpha-fetoprotein (AFP)
  • Total beta-human chorionic gonadotropin (total ß-hCG)
  • Unconjugated Estriol (uE3)
  • Inhibin-A

In pregnancies affected by Down syndrome, the levels of PAPP-A, AFP, and uE3 tend to be lower than normal while the levels of inhibin and total ß-hCG are elevated. In a pregnancy affected by other conditions such as open spina bifida or anencephaly, the level of AFP tends to be elevated. A positive integrated test is not conclusive, but does provides a Down syndrome risk estimate for your pregnancy, and indicates that further testing should be done.

Glucose challenge test: At 24-28 weeks you will be tested for gestational diabetes. Your doctor will have you drink a glucose liquid and then draw your blood an hour later. If high levels of sugar are detected in the blood, it’s an indication that your body isn’t processing sugar effectively and you may need a glucose tolerance test to confirm whether or not you have gestational diabetes.

Glucose Tolerance test: This test is offered to women with a high risk of gestational diabetes. It’s similar to the earlier screening, except you’re asked to eat a certain amount of carbohydrates days before and fast for eight to 14 hours before your test. Blood will be drawn several times: the first time to provide a base-level reading of sugar levels, and then over the course of the next few hours to get a read on how your body processes sugar over time. If you test positive for gestational diabetes, your doctor will provide lifestyle adjustments, such as a high-protein diet and exercise regimen.

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