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AFP is a protein made by the baby and secreted into the amniotic fluid and mother's blood stream. Elevated levels of AFP can be found in certain conditions such as spina bifida, anencephaly (failure of brain and skull development), abdominal wall defects, fetal death, twin gestation, or inaccurate dating of the pregnancy. An elevation of the AFP, even with a normal amniocentesis, can be associated with a higher risk of problems in the third trimester. Some of these include placental separation (abruption), preterm labor, poor fetal growth, pregnancy induced hypertension, increased risk of stillbirth, and a lack of amniotic fluid. Low levels of AFP have been associated with a higher risk of chromosome problems such as Down Syndrome. Screening of the mother's blood allows us to check for the possibility of some of these potential problems. The blood test that is drawn is called the triple screen or tri-screen. It includes an AFP, an estrogen level, and a hCG level. The tri-screen is more accurate at predicting a chromosome problem compared to the AFP alone. The majority of babies born with Down syndrome are born to women under the age of 35, even though the risk of Down syndrome is 1:270 live births. An amniocentesis is usually recommended for women who will deliver by the time they are 35 or older. For those younger than 35, the tri-screen will be positive in 60 - 65 percent of Down syndrome babies. The AFP will be elevated in greater than 90 percent of cases involving brain, spinal cord, or abdominal wall defects. If a tri-screen or AFP is abnormal, an ultrasound is recommended. An amniocentesis may also be recommended since the tri-screen is only a screening test. The amniocentesis could determine if a problem really exists. A normal triple screen does not necessarily guarantee a normal baby. The tri-screen and amniocentesis are both optional tests. A decision whether to have the test or not is usually a personal choice. A woman who would not have an abortion may still want to consider the testing in order to help prepare herself, her family, and her doctors for the birth of a baby with special needs. Even with a normal tri-screen and ultrasound, there is still the possibility of having a baby with Down syndrome. most chromosomal abnormalities other than Down syndrome are not detected by the tri-screen. An amniocentesis or other procedure called a chorionic villous sampling (CVS) are the only 100% accurate tests for Down syndrome as well as other chromosomal problems. If you choose to have this test done, the blood work should be drawn between 15 and 20 weeks, along with other prenatal laboratory work. The results are usually back in our office in approximately one week. If you are 35 or older and are going to have an amniocentesis, the tri-screen is done a few days before your amniocentesis. This will help us determine if you will be at risk of any of the third trimester problems mentioned previously.
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