Blastocyst Culture and Transfer

Recent studies confirm the fact that blastocyst transfers on day 5 have essentially equivalent pregnancy rates when compared to embryo transfers on day 3. However the advantage is significantly fewer embryos are required on day 5 to maintain these pregnancy rates. Normally, 3-4 embryos will be replaced on a day 3 transfer compared to typically only 2 blastocyts replaced on a day 5 transfer. Furthermore, equivalent pregnancy rates were obtained in spite of 20% of the patients in the blastocyst group not reaching embryo transfer. These cases should be viewed as diagnostic of embryo failure, i.e. such cycles may not have given rise to pregnancies even if the embryos were transferred on day 3. Blastocyst culture and transfer offers a way to eliminate high order multiple gestations, while maintaining high clinical pregnancy rates.

What is a blastocyst?

A blastocyst is an embryo that is approximately 5 days old following fertilization. A blastocyst contains around 100 cells that are formed into 2 distinct types, the inner cell mass that goes on to make the baby and the surface cells called the trophectoderm that goes on to make the placenta. The trophectoderm surrounds a central cavity called the blastocele. A blastocyst hatches from the Zona Pellucida (the shell of the embryo) around day 6 and begins the complex process of implantation over the next 24 hours or so.

Are you a candidate?

Candidates for a blastocyst transfer typically are younger and have a large number of eggs. On average those having 6 or more high quality embryos on day 3 are potential candidates for blastocyst culture. Other candidates may be those patients in which a multiple pregnancy would put them at extreme risk such as those with a uterine malformation. Unfortunately, blastocyst culture cannot improve the quality of an embryo. Most poor quality embryos will never become a blastocyst and even some high quality embryos will never become a blastocyst. Finally there are those rare patients whose embryos develop very poorly in the blastocyst culture media and therefore need to be transferred on day 3

Grading of blastocyst?

Basically an embryo that develops completely into a blastocyst would be considered good. However, we can grade each blastocyst based on its total number of cells, the size and shape of its inner cell mass, the size, shape and togetherness of the trophectoderm. On day 6 blastocysts should be hatched or at least have begun the hatching process.

Assisted Hatching

Recommended for: Assisted hatching entails making a small hole in the zona pellucida or shell of the embryo. Assisted hatching is recommended for those having any of the following conditions: 38 years or older, prior failed IVF cycle, fragmentation, poor embryo development, undergoing ICSI, thickened zona pellucida, or at the recommendation of the embryologist. At RMA asssisted hatching is commonly carried out on those embryos transferred on day 3.

Fragmentation removal: Fragmentation removal is performed after assisted hatching and involves removal of small cell membrane fragments from the inside of the embryo. This procedure is reserved for those embryos that have extensive fragmentation, therefore, those of poor quality. Here at RMA we rarely are required to perform fragmentation removal due to the fact that our embryos have very low percentage of fragmentation.

Success rates: Numerous studies have demonstrated that assisted hatching improves pregnancy rates and implantation rates (that is the likelihood of an embryo becoming a baby). The improvement in pregnancy rates with fragmentation removal are less clear-cut. In general, most patients having a poor prognosis of success with IVF show the most improvement with assisted hatching. Other centers have shown no improvement with assisted hatching, however, this is a highly technical procedure with many different levels of efficiency.