Genetic testing in pregnancy

Genetic testing in pregnancy – when to perform?

Genetic testing in pregnancy is not mandatory for all pregnant women, but for a specific group of moms-to-be. According to current recommendations, reimbursable prenatal tests have, among other things. women over 35. year, those who have previously given birth to a child with a genetic defect, and those with a family history of genetic defects. The first stage of diagnosis is always an ultrasound examination of the first trimester with assessment of the risk of defect in the form of a composite test (the so-called PAPP-A test). If this result raises doubts in the doctor’s mind, the pregnant woman is referred for genetic testing – either non-invasive or invasive. They are usually performed after 10.-13. Week of pregnancy (after the first trimester ultrasound). If the risk of a chromosomal defect on the PAPP-A test is between 1:300 and 1:1000, the doctor should recommend a non-invasive genetic test – NIPT. For risks greater than 1:100, invasive testing is indicated.

Genetic testing in pregnancy- invasive testing

Invasive testing is performed in women whose risk of chromosomal aberration is greater than 1:100. If the risk is between 1:100 and 1:300, alternatively, NIPT or invasive diagnostics can be performed. Among the invasive tests are cordocentesis, amniocentesis and chorionic villus biopsy.  These tests differ in the week of pregnancy in which they can be performed, as well as the material taken during the procedure. In the case of chorionic biopsy, chorionic villi are collected, in cordocentesis – blood from the vessels of the umbilical cord, and in amniocentesis – amniotic fluid. For genetic testing, the most commonly performed invasive test is amniocentesis. There is usually a wait of several days for the result of this test. The risk of complications is low. It is currently estimated at 0.1-1%. Among the most common possible complications is premature drainage of amniotic fluid.

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Invasive prenatal testing

Genetic testing in pregnancy- non-invasive tests

Non-invasive genetic testing in pregnancy-NIPT-has become increasingly popular in recent years. Manufacturers offer a number of similar tests, the general idea of which is to test a pregnant woman’s blood and analyze the baby’s DNA present in it (so-called cell-free fetal DNA- cffDNA). The success rate of non-invasive prenatal testing is up to 99%. Tests of free fetal DNA can determine the sex of the baby and the most common chromosomal abnormalities such as Down syndrome, Edwards syndrome, Patau syndrome. However, it should be borne in mind that non-invasive tests in case of a positive result require confirmation during invasive testing.

The decision regarding the choice of genetic testing is always made by the Parents, who can rely on the consultation of a perinatologist or geneticist, as well as the gynecologist in charge of the pregnancy.

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Free fetal DNA testing