PRENATAL TESTS IV: TRIPLE SCREENING

He triple screening or triple test It is one of the fundamental tests in the prenatal tests performed by the gynecologist to the pregnant woman. It is simple, it consists of a blood test in which special parameters are measured that, depending on whether they are increased or decreased, can indicate if there is any alteration in the fetus.

These substances are different hormones and proteins that are synthesized in the placenta and in the fetus:

Alfafetoproteína (AFP): in a protein that is formed in the liver of the fetus. When its concentration is increased, it may indicate that the baby has spina bifida (defect in the closure of the neural tube). In that case the performance of amniocentesis is recommended. It also rises if the pregnancy is multiple. If the levels are decreased, it could indicate Down syndrome or some other chromosomal abnormality.
Human Chorionic Gonadotropin (HCG): It is a hormone that is synthesized in the placenta. When elevated, it may indicate Down syndrome or other chromosomopathies.
Free estrogen (unconjugated): it comes from both the fetus and the placenta. Low levels are found when the fetus suffers from Down syndrome.
In some laboratories a fourth parameter is measured: inhibin A (what is called a quadruple detection test).

The results of these three compounds, are analyzed and combined, according to gestational age, race, age and weight of the woman, thus estimating the chances that the future baby may have a disease. You can rule out chromosomal diseases, neural tube defects and trisomies such as Down syndrome.

The advantage of this test is that it is not invasive and although the results it shows are purely statistical, they are quite reliable. The level of reliability is 60%.

In women under 35, it detects between 75 and 85 percent of neural tube abnormalities and 60 percent of Down syndrome cases. In women over 35, it detects 75 percent of neural tube abnormalities and cases of Down syndrome.

It can also indicate whether it is necessary or not to perform other tests that are more invasive such as amniocentesis or chorionic biopsy, to confirm the results of the analysis.

It is performed in the second trimester of pregnancy, approximately during week 16 or 17 of pregnancy.

Risks: It does not imply any risk for the mother or the baby. It is important to keep in mind that it is not a diagnostic test but an indicative one. That is why sometimes they fail and cause unnecessary anguish and alarm. In fact, only 10 percent of women with abnormal results have babies with congenital problems.