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A Guide to Second Trimester Prenatal Testing & Screening

Now that you're entering your second trimester, your doctor should be scheduling a few more blood and screening tests for you to make sure your baby's development is on track and free of complications. As always, keep in mind that screening positive for chromosomal abnormalities or fetal development problems does not necessarily mean that the tests are entirely accurate, so make sure your doctor is experienced or seek a second opinion before going ahead and following further recommended procedures. 

Quad Screening
Also known as the triple screen or Alpha-Fetoprotein (AFP) screening, the quad screening is a simple blood test designed to estimate the fetus's risk of having certain chromosomal abnormalities, neural tube defects and pregnancy complications, but is not always accurate as the false-positive rate for the independent quad screen is high. Usually performed between the 14th and 22th weeks of pregnancy, the quad screening is completely safe and painless. The only risk arises from further unnecessary diagnostic screening procedures resulting from a false positive test.

Second Trimester Ultrasound
The second trimester ultrasound is a simple sonogram screening usually conducted between the 18th and 20th weeks of pregnancy to examine fetal development and screen for fetal anatomy or pregnancy problems. It also allows the viewing of most of the baby's features and helps determine its gender, size and position. At this point you might also be able to find out your baby's sex if the screening is clear and the fetal position is appropriate. The ultrasound is both harmless and painless, and most often takes anywhere from 5 to 30 minutes to complete.

One of the most advanced prenatal diagnosis methods to date, the amniocentesis test is used to detect particular chromosomal abnormalities and serious birth defects, and involves the extraction of a sample of the amniotic fluid surrounding the fetal cells for detailed laboratory examination. It is usually conducted if a previous screening test indicated a high possibility of fetal abnormality, the mother is over 35 years of age, either the mother or both parents are carriers of genetic or recessive inherited disorders, a fetal infection is suspected, or it is necessary to examine the fetus's lung maturity late in pregnancy. This test can be conducted as early as the 13th week or as late as the 24th week based on its necessity, and the results need 10 to 14 days to be formulated and released. The amniocentesis test is both extremely accurate and entirely safe. 

Glucose Tolerance Test (GTT)
During your pregnancy, your body's hormonal balance changes, altering your ability to manage carbohydrates and sugars normally. This can potentially lead to a condition known as gestational diabetes, which can lead to the development of an unusually large baby, causing labor difficulties later on. The GTT blood test is used to screen for this problem and is often conducted between the 24th and 28th weeks or earlier if you have a family history of gestational diabetes. Luckily, most women who suffer from gestational diabetes can have a normal pregnancy simply by following a special diet and undergoing regular blood sugar tests, or taking insulin shots in some cases.