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Q&A: Prenatal Tests During Third Trimester?

What exactly will happen during the prenatal tests I get this month, and what are they looking for?

All those pee cups and needlesticks starting to blur together? This guide to the most common third trimester tests should help you keep things straight. You’ll definitely receive all screenings with a*, and should discuss the others with your doctor.

[ ] Urine Tests*
At every appointment, you’ll give a urine sample to be screened for glucose (elevated levels can be a sign of gestational diabetes) and protein (a possible indication of preeclampsia or a urinary tract infection). If either shows up in your urine, your doctor will likely order order additional testing.

[ ] Ultrasound*
You'll probably have at least two ultrasounds during your pregnancy. At about 10 weeks, an ultrasound can detect afetal heartbeat and confirm that the pregnancy is uterine (as opposed to ectopic ortubular). A more detailed ultrasound anatomy scan (also called a level two ultrasound) is performed between weeks 18 and 22. Your baby will be measured from crown to rump and around the waist and head to confirm proper growth, and the kidneys, bladder, stomach, brain, spine, sex organs and four chambers of the heart will be checked for normal development and any potential problems. The ultrasound technician will also check amniotic fluid levels, placenta location and fetal heart rate. If necessary, a late-pregnancy ultrasound can check for pre-term labor by measuring cervix length.

[ ] Amniocentesis
Recommended for women overage 35, this test, performed between weeks 15 and 20, analyzes amniotic fluid from the uterus for Down syndrome, genetic diseases such as Tay-Sachs and sickle cell anemia, and neural tube defects like spina bifida. It also can be used after week 32 to determine if baby’s lungs are mature enough to function outside the womb.

[ ] Glucose Tolerance Test
Between weeks 24 and 28, almost all women are screened for gestational diabetes mellitus (GDM). If you have specific risks, you might take it earlier. The test can’t diagnose GDM, but will determine whether further testing is necessary.

[ ] Group B Strep Test*
This test, given to all women around week 36, screens for harmless bacteria in the rectum and vagina that can be dangerous if transmitted to baby during delivery.

[ ] Nonstress Test
If you’re overdue or at risk of premature labor, or if there are signs of fetal distress, your doc may perform a nonstress test to measure fetal heart rate and movement and uterine activity. This test can be done anytime after 24 to 26 weeks, but is most commonly performed late in the third trimester.

[ ] Biophysical Profile
Usually performed with the nonstress test in the third trimester, this profile shows the baby’s heart rate, activity level, breathing movements, muscle tone and the amount of amniotic fluid in the uterus. Your doc might recommend it if you’re carrying multiples, are past your due date, or have risk factors such as high blood pressure or kidney or heart disease.