Preimplantation genetic screening (PGS) is performed on embryos from in vitro fertilizations, to select only viable embryos that are more likely to be implanted and result in a healthy baby, with no genetic diseases. In couples with advanced maternal age, PGS makes sense, as the mother's age can have a great impact on the health of the baby.
Risks in Advanced Maternal Age
All women are born with a number of eggs. When they reach maturity, the eggs are released, one per month, during ovulation. The body selects the best eggs to release first and for this reason, the babies that are born to younger mothers are less likely to have genetic diseases or other chromosomal issues.
In babies resulting from mothers with an advanced age, there are several risks, the most common being aneuploidy. Aneuploidy is more common (40 percent) in mothers over 40, and 20 percent in mothers between 35 and 39; the chromosomes in the eggs remaining in the body of the woman may not be able to divide normally, resulting in an additional chromosome or the lack of one. PGS can detect such abnormalities in the embryo.
Trisomy and Advanced Maternal Age
Trisomy, more commonly known as Down's syndrome, is a type of aneuploidy, which indicates that there are 3 identical chromosomes in the same embryo. Trisomy is more common in women over the age of 35. PGS can detect the presence of these identical chromosomes. In pregnancies that are obtained naturally, the detection of trisomy can only be done when the fetus is 16 weeks old. This abnormality can also cause spontaneous abortion.