Blastocyst Culturing

Blastocyst culturing is a technique to grow embryos beyond the 3 rd day of culture. Typically we transfer embryos into the uterus ~3 days after the egg retrieval. On the 3 rd day, embryos generally are between 6-8 cells. We now have the ability to culture the embryos 2 additional days. During this additional culture period, the embryos continue to grow to become "blastocysts."

The natural process of embryo development begins with the fertilization of the egg in the outer aspect of the fallopian tube. As the newly-formed embryo develops, it moves slowly toward the uterine cavity where it will ultimately implant. This process takes approximately 6-7 days. When the embryo reaches the "blastocyst" stage, it is ready to implant.

	Why should we consider blastocyst transfer?
	In certain patients, the advantage of blastocyst culturing is to allow optimal selection of embryos for transfer resulting in an increased implantation rate per embryo transferred. However, it is important to understand that this technology may not necessarily increase your chance for pregnancy. The main advantage is that fewer embryos may be transferred to eliminate the possibility of triplet and quadruplet pregnancies, while maintaining a high pregnancy rate.
	Is it for everyone?
	NO. Generally speaking, this procedure should be limited to patients with excessive numbers of embryos (greater than 10) in which case further selection of embryos beyond the day 3 stage would be advantageous. As a general rule, patients under the age of 37 are candidates for this culturing technique. We do not recommend this procedure to older patients because the risk of having no blastocyst embryos for transfer is too great.
	What percentage of embryos will grow to the blastocyst stage in culture?
	For younger patients, up to 50% of all embryos will continue to grow to the blastocyst stage. However, 10% of patients will not have an opportunity for embryo transfer due to the absence of blastocyst development. As patients get older, fewer and fewer numbers of embryos are capable of developing in culture to the blastocyst stage.
	What are the risks of blastocyst culturing?
	There are two main concerns with blastocyst culture: Some patients may have no embryos develop to blastocyst and thus lose the opportunity for a transfer. The number of embryos for freezing and the survival of embryos after thawing will decline, potentially lowering the overall pregnancy potential of a single stimulation/egg retrieval treatment cycle.
	How do we know if we should seriously consider it?
	If you are younger than 37 years old with a normal day 3 FSH level and have a strong desire to avoid triplet pregnancy, then you should seriously consider it. If you have an absolute reluctance to selective fetal reduction, then you have even more reason to consider blastocyst culturing. If you are open to selective fetal reduction, then blastocyst culturing is not necessary. A decision to transfer less embryos on day 3 can also be made.
	Are there any limitations to blastocyst culturing?
	YES, If you have less than four 8-cell quality embryos on the 3rd day of culture, we do not recommend proceeding with blastocyst culturing even if you so desire it. With blastocyst culturing, we are not able to freeze as many embryos because of poor embryo development to the blastocyst stage. Also, there appears to an increased risk of identical twinning with blastocyst culturing (including the possibility of conjoint twinning where the babies may be connected and share some organs). Fortunately, the risk of identical twinning is very low (<5%).
	Would the embryos that arrest in culture prior to the blastocyst stage have arrested in the uterus?
	There is no possible way to completely know this answer. We believe that embryos that do not survive in culture would be less likely to survive or implant in the uterus.

Embryo Co-Culturing

Embryo co-culturing is a technique initiated in the UCSF IVF laboratory about 2 years ago to improve the overall quality of embryos prior to your transfer. Several other IVF programs in the world have used this technique since 1996. It involves the use of human granulosa or endometrial cells that may secrete nutritional products to assist the growing embryos in order to improve their chance for survival.

	Who should consider this technique?
	We only recommend this technique to patients who have had previously failed IVF cycle(s) with poor embryo quality either here at UCSF or at another program. We do not recommend that patients select this option if they have never been through IVF before or if they have had treatment cycles with excellent embryo quality in the past.
	Why should we be concerned about poor embryo quality?
	An important concept to understand is that your likelihood of achieving pregnancy regardless of your age depends on the overall quality of your embryos. If you have generally good embryo quality, then you have a higher chance of conceiving from your IVF treatment cycle. Conversely, if you have generally poor embryo quality, then your chance for success goes down.
	What is the experience of the UCSF IVF laboratory with the co-culture technique?
	The UCSF IVF laboratory initiated the co-culture technique using these cells in 1999. To date, we have had 35 IVF cycles completed using co-culture. Using the co-culture system, we have seen an improvement in embryo quality and relative growth of the embryos 72 hours after egg retrieval (Remember that eggs fertilize within 18-24 hours after egg retrieval).
	What are the risks of co-culture?
	The risks associated with co-culture are unknown at this time. Because it has never been tested extensively, there is no information regarding children born of co-culture using these specific cells. It is because of this fact that we remain cautious about using this approach on patients who clearly may not benefit from this technique. It is important to understand that some patients may not have improvement in their embryo quality despite the use of co-culturing.
	If co-culture is recommended by our UCSF physician, will all of our embryos be exposed?
	If you and your physician agree to use co-culture for your IVF treatment cycle, then we will incubate all of your embryos in the co-culture environment as soon as fertilization has been confirmed by our embryologists. We will continue co-culture until the day of your embryo transfer.
	Is it possible to freeze co-culture embryos?
	Yes, we do not believe that co-culture will affect the ability of your embryos to freeze well. We use the same standards for freezing co-cultured embryos as we do for standard cultured embryos. If your embryo quality is improved with co-culture, there is a greater likelihood that we will be able to freeze more embryos for you.