What Is and Isn’t True
One of the most misunderstood treatment choices for infertility is preimplantation genetic screening, known as PGS. PGS is a screening procedure that checks the number of chromosomes in an embryo, using a few cells from its outer layer. The test looks for abnormalities like too few or too many chromosomes. Chromosome abnormalities are the major cause of failure to implant in IVF treatment and of miscarriages.
Using PGS helps ensure that healthier embryos are transferred so your chances of success are better. Is PGS right for you? Your fertility specialist can recommend whether you need it or not. Here are some common misconceptions about PGS.
PGS is Only for Older Women
It is true that women 35 and older tend to have lower-quality eggs than younger women, and that chromosomal abnormalities increase as women get older. That’s why Down syndrome, which is caused by an extra copy of chromosome 21, is much more common among children of women 40 and older than among children of younger women. But maternal age is not the only reason to screen with PGS. Chromosome problems may happen in younger women, too. If a couple has had multiple failed IVF cycles, recurrent pregnancy loss, unexplained infertility, or a family history of chromosomal abnormalities, PGS may be helpful.
PGS Can Damage Embryos
Fertility treatment is advancing every year. In the past, fertility clinics performed PGS on cells biopsied from day 3 embryos. The day 3 biopsy technique has been shown in several studies to have harmful effects on the embryo. As a result, most clinics have moved to testing cells from a blastocyst, which is the embryo’s stage of development at day 5 or 6. A few cells are removed from the layer that will form the placenta called the trophectoderm, rather than the inner cell mass which becomes the fetus, so the embryo is much less likely to be harmed. PGS at this stage usually requires freezing the embryos and transferring them in a subsequent cycle as it takes some time to get the results back from the testing.
PGS is Used for Sex Selection
PGS screening detects if the embryo is XX (female) or XY (male). This can be important for choosing a healthy embryo if the couple has a family history of a sex-linked genetic disease. Using PGS to select your child’s gender is controversial. Many fertility clinics will not reveal the gender of a PGS-screened embryo until after it has been transferred and has implanted. Other fertility clinics will cooperate with gender selection if the couple wants that. If you want to determine the sex of your child, make sure you choose a fertility clinic that performs gender selection for family balancing purposes.