To increase the chance of a healthy pregnancy, preimplantation genetic diagnosis (or preimplantation genetic screening) can be used in IVF programs
Preimplantation genetic screening is an additional procedure in the IVF cycle.
For screening test, on the 5th day of embryo development, an embryologist performs a trophectoderm biopsy — taking a small number of embryonic cells. Obtained samples are sent to the genetic laboratory for further examination. After the biopsy, the embryos are frozen and stored until the genetic study results are obtained and the time of transfer into the uterus is appointed.
There are various methods to study the chromosomal status of the embryos. We prefer the most advanced and reliable technique — NGS (next generation sequencing, or high-throughput sequencing), based on determining the DNA sequence, which offers a means for deciphering genetic information encoded in the DNA of the embryo.
Certainly, embryologist chooses the best embryos for transfer — actively developing and having the “correct appearance”, but using PGD provides the possibility to «look inside» the embryo to make sure that the embryo has the normal set of chromosomes. The transfer of good (from the standpoint of morphology, or appearance) and healthy (having 46 chromosomes) embryo into the uterus reliably increases the chances of pregnancy in the IVF cycle.
HOW ARE THE RESULTS OF PREIMPLANTATION GENETIC SCREENING INTERPRETED?
According to the results of the genetic studies, embryos will be classified as:
- EUPLOID— “healthy” embryos having 46 correctly structured chromosomes; such embryos are transferred into the uterus
- ANEUPLOID — embryos with abnormal number of chromosomes (for example, 47 chromosomes instead of 46); such embryos are not subject to transfer
- MOSAIC EMBRYOS.Mosaicism is the condition when part of the embryo cells has the correct chromosome set, and some — abnormal. The decision on transfer the embryo into the uterus is made depending on the ratio of normal and abnormal cells. In such cases, we recommend genetics consultation
- EMBRYOS WITH «NO SIGNAL» — in 5% of cases, genetic study does not allow to determine the chromosomal set of the embryo. In such cases, repeated biopsy of the embryo may be recommended.
Consult your fertility specialist to make a decision on the necessity of preimplantation genetic diagnosis!