PGS, preimplantation genetic screening, can be used to be sure only embryos with normal chromosomes are transferred back into the uterus. It can also be used for family balancing.
Many patients wonder if we can determine if the embryos going back into them are normal and wonder if the sex of the embryos can be determined prior to being placed into the uterus.
In general, the chromosomes and sex of the embryo cannot be determined in routine IVF. We can only determine the likelihood of implantation by the quality of the blastocysts. At Fertility Center of New England, we only transfer day five embryos called blastocysts. Embryos that have been grown for five days allows us to better choose embryos with a high chance of implantation; this is becoming the industry standard. On day three the embryos are usually 6 to 8 cells and their chance of implantation cannot be easily determined.
In addition, when embryos are grown to blastocysts which Fertility Centers of New England has been doing for nearly a decade, they are able to be easily biopsied to determine chromosomal number and sex of the embryo.
How does PGS work?
The day five embryos or blastocysts have started to differentiate into the fetal cells and the placental cells. Placental cells are on the outside of the embryo and a few cells of the potentially placental tissue can easily be removed without damaging the embryo. Once the cells are removed they are sent for a full chromosomal number analysis; this will include the number of X and Y chromosomes. The embryos are then cryopreserved while we await the results.
Cryopreservation of the embryos appears have no negative effects on the embryos.
In fact, embryos that are cryopreserved and then thawed have a lower chance of having malformations than if the couple were to conceive on there own.
Within a few days of the biopsy the full chromosome analysis results are sent to the physician. At this time the physician will meet with his or her patient and discuss the results. Unfortunately, as women age there is a higher chance of abnormal embryos. Certainly, women who are over the age of 37, and women who had recurrent pregnancy loss might consider this option. Certainly patients with a known genetic defect or are carriers for genetic illnesses can have preimplantation genetic diagnosis as well. This is done in a similar fashion.
Finally, in couples who already have a daughter or son, we offer PGS to help the couple know the sex of the embryos that are replaced. We call this family balancing. In accordance with ASRM guidelines, we do not allow patients to choose the sex of their child if they have not had a child, but to allow family balancing if they already have at least one child.
At Fertility Center of New England, we offer PGS at a very reasonable cost to help patients be sure they have normal embryos transferred during an IVF cycle. If you have more questions about PGS, please contact us.