If you are pregnant your health care provider may recommend you to go for prenatal diagnostic testing. Prenatal diagnostic testing involves testing the fetus before birth to determine whether the fetus has certain abnormalities, including certain hereditary or spontaneous genetic disorders. Measurement of certain substances in the pregnant woman’s blood helps medical health professionals estimate the risk of genetic abnormalities in the fetus, such as Down syndrome, chromosome abnormalities, brain or spinal cord defect, and some rare genetic disorders.
Normally ultrasonography and blood tests are done as part of prenatal diagnosis. The Test DNA Prenatale are safe and helpful in determining whether more invasive prenatal genetic tests are required. The more invasive tests include Chronic Villus Sampling and Amniocentesis. These invasive tests are done when couples have an increased risk of having a baby with a genetic abnormality.
First trimester prenatal diagnosis
During the first trimester, screening prenatale consists of blood tests for measuring the levels of pregnancy-associated placental protein A, produced by the placenta, and beta-human chorionic gonadotropin in the pregnant woman’s blood. The blood tests are done to estimate the risk of Down syndrome. They are usually done at about 11-14 weeks of pregnancy. A new blood test called cell-free fetal nucleic acid testing is also done these days. During this test, small fragments of the fetus’s DNA, which are present in the pregnant woman’s blood in tiny amounts, are analyzed. This test helps in accurately determining the risk of Down syndrome and some other chromosomal abnormalities in couples with a high risk of having a fetus with a chromosomal abnormality. The test is done as early as 10 weeks of pregnancy but can also be done later.
Ultrasonography measures a fluid-filled space near the back of the fetus’s neck called fetal nuchal translucency. It helps in estimating the risk of Down syndrome and certain other chromosomal abnormalities. Ultrasonography can also show whether the space at the back of the fetus’s neck is enlarged. In case it is, there is a high risk of these abnormalities.
First trimester screening provides fast results. And with the earlier results, abortion, if desired and required, can be done.
Second Trimester Screening
During the second trimester, markers in the pregnant woman’s blood are measured. Important markers include Alpha-fetoprotein, Estriol, Human Chronic Gonadotropin, Inhibin A. High level of Alpha-fetoprotein level in pregnant woman indicates the risk of having a baby with neural tube defect of the brain or spinal cord, or a baby with the birth defect of the abdominal wall, and later pregnancy miscarriages such as slowed growth or death of the fetus.
Ultrasonography is done if blood tests indicate abnormal level of alpha-fetoprotein in the blood of the pregnant woman. It helps to know the length of the pregnancy, determining whether more than one fetus is present, determining whether the fetus has died, and detecting any birth defects.
CVS and Amniocentesis are done only when the woman has a very high risk of having a baby with chromosomal abnormalities. These days many doctors and couples choose non-invasive diagnosi prenatale as it is safe and doesn’t pose any risk to the pregnant mother and to the growing baby.