Examining an Embryo with PGD
To examine an embryo for gender and/or genetic disorders/chromosomal irregularities, the technician first extracts one of the embryo’s cells. This is done by boring a microscopic opening in the egg’s outer mucus layer with a laser beam. Next, a single cell is removed with gentle suction.
This cell is examined for single-gene diseases and gender, generally using the fluorescent in situ hybridization (FISH) process. After the biopsied cell is examined, the couple is given an embryology report, including the number of viable embryos, their gender and condition. If the embryos appear to have normal chromosomes they can be:
- transferred to the woman’s uterus or
- cryopreserved for future use (see options for extra embryos).
While the single cells are being assessed, the embryos are kept in a culture where they grow further. They are usually transferred to the patient’s uterus via IUI at about day 5.
After receiving the embryo report, the couple have to make a big decision regarding how many embryos to transfer to the uterus. With their doctor’s advice, they decide, and the rest of the healthy embryos can be frozen for later use.
Although in typical cases of IVF without PGD, more embryos may be transferred if a woman is of “advanced age” or a history of fertility problems, with PGD, the recommended number is generally two because these embryos have been checked for abnormalities, and the ones chosen for transfer are most likely healthy, viable embryos that can develop well into babies.
Any more than two embryos would increase the risk of triplets or more, and all the potential complications of multiple births. A couple may opt for just one embryo, but their chances of pregnancy are reduced; considering what couples have gone through physically and emotional, most want to optimize their chances of a successful pregnancy with two embryos.