In the early days of IVF, fertility centers would visually inspect embryos prior to IVF transfer to settle on the best candidates.
Were the embryos uniformly shaped? Growing as they should? Today, your fertility specialist may talk with you about preimplantation genetic screening, or PGS. Looks can be deceiving. Even after successful fertilization and an A+ outward appearance, not every embryo is genetically sound.
PGS allows us to “count chromosomes”, verifying that each pair of 22 autosomes is present and accounted for prior to the IVF transfer.
If you have experienced recurrent pregnancy loss, or one or more failed IVF cycles, this IVF lab technique can help you achieve a successful pregnant. Women concerned with age-related chromosomal abnormalities may also consider PGS.
Counting on PGS for comprehensive chromosomal analysis
The PGS process starts on Day 5-6 after fertilization with a trophectoderm biopsy. IVF embryologists will remove about 100 cells from what will become the placenta (the trophectoderm layer) and then send theses preserved cells to a partner reference lab for analysis. The reference lab will examine the chromosomal make-up of the biopsied cells for errors, like chromosomal translocations and aneuploidy, extra chromosome copies found in the cell. Back at our Dallas Fertility Center the embryos are briefly frozen to stop growth until the PGS results are back from the reference lab.
Why Sample the Embryo’s Cells on Day 6?
At a time when cell multiplication is rapidly progressing, we can verify that each of the 22 pairs of normal chromosomes (plus the sex chromosomes, X&Y) are present and will likely lead to the development of a normal embryo. The reference lab will also indicate which embryos have extra or deleted chromosomes and/or balanced translocations that indicate a poor prognosis for a healthy pregnancy
Inside the cell’s nucleus we find the familiar ladder-like structure that holds 22 pair of non-sex chromosomes and one pair of X and Y sex chromosomes. PGS testing looks at these chromosomes to uncover chromosomal differences that can cause Down syndrome, or trisomy 21.
Example: a child with Down syndrome has an extra 21st chromosome.
Dallas Fertility IVF Center, our partner lab, has also started participating in research involving microscopes that rely on time-lapsed photography and an advanced software program to analyze embryonic development.
“PGS levels the playing field”
Dr. Karen Lee, a board certified reproductive endocrinologist, explains how PGS levels the playing field for her advanced maternal age patients.
“Examining the DNA of an embryo enables us to identify and transfer only those that are genetically and chromosomally sound. Suddenly, a 41-year-old has the chromosomal potential of a 33-year-old.”
Dr. Lee says that more and more of her peers are relying on PGS to improve IVF success rates for their patients.
“Luminaries in reproductive medicine are routinely offering frozen embryo transfer, the new standard after trophectoderm biopsy,” adds Dr. Lee. “Vitrification and a delayed transfer cycle allow the uterus to return to a normalized physiological state.”
To learn more about the benefits of PGS for improved IVF success rates, as well as PGD for inheritable genetic disorders, contact us at Dallas-Fort Worth Fertility Associates.