A simple blood test of the expectant mother is enough to determine the sex of the baby.
Until now, knowing the sex of the fetus during the first trimester of pregnancy could only be done through a chorionic villus biopsy or amniocentesis. The result was very reliable, but the process for obtaining it involved certain risks. Another method used to find out the baby’s gender is ultrasound, although it is not considered reliable enough until the second trimester of pregnancy.
Currently, the detection of free (non-cellular) fetal DNA in the blood stream of pregnant women does not allow prenatal genetic diagnosis to be offered without risk to the fetus.
Between the 7th and 8th week of pregnancy, the percentage of DNA of fetal origin that circulates in the mother’s blood is 6%. Now is the perfect time to do the analysis.
Today, detection of free fetal DNA sequences is possible thanks to molecular biology techniques performed in hospitals. The first clinical applications are the determination of the sex of the fetus and the fetal blood group, thanks to a blood test from the mother.
What is free (non-cellular) fetal DNA?
DNA is the genetic material found in every cell in our body. The DNA pattern, on the other hand, constitutes the genes responsible for our individual characteristics, such as the color of our hair or our eyes, but also of any genetic disease from which we may suffer or which we are carriers.
Free fetal DNA is the genetic material that comes from fetal cells and that circulates freely in the mother’s blood during pregnancy. The exact mechanism of how this fetal DNA gets into the mother’s blood stream is still unknown, but it is known to increase throughout pregnancy and only two hours after delivery, it is no longer detectable.
How is free fetal DNA used to determine the baby’s gender?
To determine the baby’s sex using free fetal DNA, a sample of the mother’s peripheral blood is extracted from the 8th week of pregnancy, taking a blood test equivalent to a conventional blood test. Then, thanks to a molecular test, the laboratory seeks to identify the presence of specific genes in a male individual. If it detects them, the baby is a boy. Otherwise, the baby is a girl.
The usefulness of determining free fetal DNA
The test can be performed on any pregnant woman who needs to know the gender of her child. The determination of free fetal DNA is particularly indicated in women with a history of the transmission of sex-related diseases.
Detection of fetal Rhesus is also useful if fetal hemolytic disease is suspected (in Rhesus negative women pregnant with Rhesus positive babies).
Reliable from the 8th week of pregnancy
This test can be performed from the 8th or 9th week of pregnancy since, from this moment, the quantity of free fetal DNA present in the maternal blood is significant. Before performing the test, it is important to confirm the gestational age through an ultrasound.
