In Vitro Fertility Goddess

Breakthrough in Embryo Screening

15 June, 2008

Source: Human Reproduction

The single focus for fertility-challenged couples when they undergo IVF treatment is have just one healthy child emerge from this arduous and emotionally draining procedure. But more often than not, multiple births occur with unintended health and societal consequences. The main reason lies in the fact that more than one embryo is implanted to increase the chances of a successful pregnancy. Fair enough, even if some IVF clinics promote multiple implants to increase their pregnancy success rates and attract new clients. The implant procedure is also due to the fact that current testing methods cannot work out with any precision or degree of certainly which particular embryo has the potential to not only implant by turn into a healthy baby.

But that could be about to change after a team of scientists from Australia and Greece discovered which genes inside blastocysts are responsible for their successful implantation.

For this study, 8-20 trophectoderm cells were collected from blastocysts on day 5 from 48 consenting patients and the biopsied blastocysts were transferred on day 6. A clinical pregnancy rate of 52% was achieved with 35% implantation rate and the birth of 37 babies. Fluorescent polymerase chain reaction (F-PCR)-based DNA fingerprinting and micro-array mRNA analysis techniques were used to test trophectoderm cells of blastocysts and cord blood or cheek buccal cells from newborns. To identify the key genes expressed in viable embryos, biopsy material from pregnancies (all embryos implanted) was compared with pregnancy failures (none implanted). Specimens from other pregnancies (where some transferred blastocysts implanted while others did not) were analysed to determine which specific sibling blastocyst produced a baby.

Over 7300 gene transcripts were uniquely associated with blastocysts that implanted. Of these, the genes expressed most significantly were those associated with attributes expected of a robust and metabolically active embryo: cell adhesion, communication, metabolic processes and response to stimuli. In this study, implantation failures resulted from the transfer of non-viable blastocysts. Since viable blastocysts can be lost through unintentional failures of the embryo transfer process, some questions remain. Nevertheless, this novel testing strategy most certainly advances our understanding of gene expression patterns that are important for embryo viability.

Future studies promise to corroborate genetic testing with established methods for identifying viable embryos. This technology will unavoidably increase an embryologist's analytical time for each patient cycle, but clearly, genetic analysis alone or in combination with recognized methods has the potential to identify the unique pattern of gene activity for a particular embryo. The ability to recognize embryos best suited for single embryo transfer or cryopreservation that will lead to implantation and the birth of a single healthy baby will minimize the risk of multiple pregnancies.