Second Trimester Tests During Pregnancy
Glucose screening: Typically done at 24 to 28 weeks, this is a routine test for pregnancy-induced diabetes, which can result in overly large babies, difficult deliveries, and health problems for you and your baby. This test measures your blood-sugar level an hour after you've had a glass of a special soda. If the reading is high, you'll take a more sensitive glucose-tolerance test, in which you drink a glucose solution on an empty stomach and have your blood drawn every hour for 2-3 hours.
Amniocentesis: This optional test is usually performed between 15 and 18 weeks of pregnancy (but can be done earlier) for women who are 35 or older, have a higher-than-usual risk of genetic disorders, or whose MSAFP or multiple marker test results were suspicious. The procedure is done by inserting a needle through the abdomen into the amniotic sac and withdrawing fluid that contains fetal cells. Analysis can detect neural tube defects and genetic disorders. The miscarriage rate after amniocentesis varies depending on the experience of the doctor performing the procedure, averaging about 0.2% to 0.5% at 15 weeks, but the test can detect 99% of neural tube defects and almost 100% of certain genetic abnormalities.
Fetal Doppler ultrasound: A Doppler ultrasound test uses sound waves to evaluate blood as it flows through a blood vessel. Fetal Doppler ultrasound can determine if blood flow to the placenta and fetus is normal.
Fetoscopy: Fetoscopy allows a doctor to see the fetus through a thin, flexible instrument called a fetoscope. Fetoscopy can detect some diseases or defects that cannot be found by other tests, such as amniocentesis, ultrasound, or chorionic villus sampling. Because fetoscopy carries significant risks for the mother and fetus, it is an uncommon procedure that is only recommended if there is a much higher-than-normal chance that the baby will have an abnormality.