MAXIMIZING IVF SUCCESS RATES
Blastocyst culture and transfer is an important technique developed for in vitro fertilization (IVF) that maximizes pregnancy rates while minimizing the risk of multiple pregnancy. The ability to grow embryos for five or six days to the blastocyst stage of development in the laboratory, rather than the traditional three days, allows Shady Grove Fertility’s embryology team to determine, with greater certainty, which embryos are really the “best” in terms of their potential for implantation and ultimately pregnancy.
Consequently, blastocyst culture makes it possible to select the best one or two blastocysts vs. two or three (or rarely four) early embryos to transfer back to the mother. This reduces the occurrence of potentially risky multiple births. Shady Grove constantly strives to improve IVF success rates through the steady refinements of clinical and laboratory techniques. Clinical blastocyst culture and transfer is an important step in that evolution.
BLASTOCYST CULTURE AND TRANSFER
Traditionally, embryos had been transferred to the uterus on the second or third day of development after in vitro fertilization and initial embryo cell division. Transferring embryos this early had been a balance between maximizing the degree of embryo selection available through longer culture in the IVF Lab, versus minimizing the exposure of the embryos to culture media which, in the past, could only sustain growth for two to three days.
The culture media of the past was more of a “one size fits all” option and as a result the dynamic processes of embryo development were not able to be taken into account. Because of this, blastocyst growth in vitro had always been suboptimal. But advances in culture media now allow physicians and embryologist to take into account the myriad changing needs of the developing embryo in vitro.
After five days of growth, the cells of the embryo should have divided many times over, and have begun to differentiate by function. The embryos that survive to this stage of development are more likely to be strong, healthy, and robust.
Three important factors previously limited the number of embryos that could survive to this stage:
First, the inherent “health” of any embryo will dictate its ability to continue to grow and divide. Several eggs may have initially fertilized, but only a few will progress to the four-cell stage on day two in culture, fewer still to the eight-cell stage on day three in culture, and even fewer will develop into blastocysts. Simply put, this self-selection can be viewed as “survival of the fittest.”
The second limiting factor in preventing continued growth of embryos in culture had been the culture media itself. Researchers have identified shortcomings of the in vitro culture environment and have lead to developments in new culture solutions called blastocyst media. These are rich in life-sustaining nutrients that give the embryos every chance to reach there full inherent potential. As a result from egg collection onward, embryos will now be exposed to specific media that are designed to meet the nutritional requirements of each stage of development.
Third, even with embryos of good growth potential and optimal culture media, the experience and expertise of the laboratory embryologists doing this important work is critical to achieving good blastocyst development. It is here that the embryologists at Shady Grove Fertility excel. They, as opposed to many other laboratories who have tried but then abandoned the rigors of blastocyst culture, have optimized the opportunities for patient success in their IVF cycles and in their quest to build their families.
BENEFITS OF BLASTOCYST TRANSFER WITH IVF
Let’s use an example. Historically, if a woman has 15 eggs retrieved, an average of 10 would fertilize after one day. It is impossible to determine at this point which of these 10 are most likely to implant and develop into a baby. Perhaps all will, but perhaps not. On the previous traditional day of embryo transfer (day three), 5 of the 10 embryos may be developing into vibrant, growing embryos. The others may have slowed or stopped their development altogether as naturally many eggs and embryos are abnormal.
In this example, we are left with several embryos that still look like they may have excellent potential. Which ones to transfer? Which ones are really the “best”? Two additional days in the blastocyst culture medium allows the natural winnowing process to continue. Thus, after 5 or 6 days of growth in the laboratory, only two or three of the original ten embryos may remain viable, showing their inherent potential. We now know the best embryo(s) to transfer and that waiting for day 5 provides the best chance of determining this information.
Embryos transferred at the blastocyst stage have made it through key growth processes and typically offer a greater chance of implanting. Without compromising pregnancy rates, we need only return one or two blastocysts to the mother instead of the typical two or three early embryos. In addition, the fewer embryos transferred, the more that may be available for cryopreservation for future use in frozen embryo transfer (FET) cycles.
A significant benefit of blastocyst culture and transfer is the reduction of multiple births that can result from in vitro fertilization. This means that the many obstetrical complications that may arise from multiple pregnancies can be minimized. It is especially important in helping patients avoid having to make the difficult personal and ethical decisions regarding selective reduction.
IS IVF WITH BLASTOCYST TRANSFER RIGHT FOR EVERYONE?
Decidedly not, in thinking of the example above, patients who have fewer oocytes retrieved, fewer fertilized or fewer dividing embryos by day three in culture have no advantage using blastocyst culture, since little is to be gained in further embryo “self selection.”
It is important to note that this new blastocyst culture media does not improve the health or viability of an individual embryo which is not otherwise able to sustain five days of growth and then implant; rather it allows embryos capable of sustained growth to continue in culture and reach their maximum inherent capability.
LET US HELP YOU DECIDE
In this field of medicine, continued refinements and change offer greater opportunity for infertile couples. Blastocyst culture is one important step and one at which Shady Grove Fertility excels.
It is exciting for us to be able to offer our patients this promising state-of-the-art technique, as it provides us the ability to further tip the balance of success versus risk in favor of couples when we assist them in their pursuit of parenthood. Be most assured that whether if day 5 or 6 transfer is recommended for you, it is a decision made by the experienced and expert clinical and laboratory teams aligned to give you the best individualized advice for a safe and successful outcome.