Why is the Triple Test Performed and What are its Results?
Results are obtained by entering the three hormone values determined in the blood and the aforementioned factors into a special computer program.
The triple test is performed between the 16th-18th weeks of pregnancy and is also known as the second-trimester screening. It is a blood test performed by examining three factors in the mother's blood. The purpose of performing the triple test is to evaluate the baby in the womb for Down syndrome and to take certain precautions based on the results. Similar to the double screening test, this test also investigates the risks of developing Down syndrome and Edwards syndrome. A small amount of blood is taken from the expectant mother for the triple test, and the hormones AFP, Hcg, and uE3 are investigated and measured in the collected blood. The values of these hormones change according to the week of pregnancy, so MOM values, specifically calculated for the current week of pregnancy, are determined. The factors considered when calculating the test result include the expectant mother's age, diabetes, race, and whether she smokes. The result is only a probability and does not provide a definitive diagnosis for the baby. High values in the triple test result do not confirm a diagnosis; therefore, the diagnosis will be confirmed by CVS or amniocentesis. The probability of having a baby with Down syndrome is a result like 1/2300. However, if this result is evaluated as 1/270, and more commonly 1/220 or 1/200, it indicates a high probability of having a baby with Down syndrome. The triple test helps to identify approximately 60% to 70% of babies with Down syndrome.
If the result of the triple test indicates a high risk for Down syndrome, a definitive diagnosis is required to determine whether the baby in the womb has Down syndrome or not.
For this reason, amniocentesis is performed to examine the baby's chromosomal structure, meaning a sample is taken from the fluid surrounding the baby in the womb, or a blood sample is taken from the umbilical cord for chromosomal analysis to confirm the diagnosis. Amniocentesis is most commonly performed before 5 months of pregnancy because the risk of complications is lowest. The fluid obtained through amniocentesis is examined in the laboratory to determine if it is within normal limits. I would also like to point out to expectant mothers that not every high triple test result indicates that the baby has Down syndrome; however, it is known that 1 in 100 high-scoring tests actually have Down syndrome, meaning the risk of Down syndrome in every one hundred high triple tests is 1%. Therefore, expectant mothers do not need to worry if their triple test result is high; waiting for amniocentesis, which confirms the diagnosis, is the most appropriate step.
