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FAQ: Blastocyst Culturing
What is blastocyst (embryo) culturing?
Blastocyst culturing is a technique to grow embryos beyond the third day of culture. Typically with IVF, embryos are transferred into the uterus about three days after the egg retrieval, which is several days earlier than would occur in nature. On the third day, embryos generally are between six to eight cells. We now have the ability to keep the embryos two additional days in a culturing material before implantation in the uterus. During this additional culture period, the embryos continue to grow to become "blastocysts."
What are the benefits of blastocyst transfer?
In certain patients, blastocyst culturing allows optimal selection of embryos for transfer, resulting in an increased implantation rate. However, 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.
Who should consider this procedure?
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 three 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 of the high risk of having no blastocyst embryos for transfer.
If you are younger than 37 years old with a normal day three FSH level and have a strong desire to avoid triplet pregnancy, then you should seriously consider blastocyst culturing, especially if you have an absolute reluctance to selective fetal reduction. If you are open to selective fetal reduction, then blastocyst culturing is not necessary. A decision to transfer fewer embryos on day three also can be made.
What percentage of embryos will grow to the blastocyst stage in culture?
For younger patients, up to 50 percent of all embryos will continue to grow to the blastocyst stage. However, the embryos in 10 percent of patients -- especially older women -- will not develop to the blastocyst stage in culture.
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.
What are the limitations of blastocyst culturing?
If you have fewer than four to eight embryos on the third day of culture, we do not recommend proceeding with blastocyst culturing, for with this procedure we are not able to freeze as many embryos because of poor embryo development to the blastocyst stage. Also, there appears to be 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. However, this increased risk of identical twinning is less than 5 percent.
Would the embryos that stop growing in culture prior to the blastocyst stage have stopped growing in the uterus?
There is no possible way to know the answer. That said, we do believe that embryos that do not survive in culture would be less likely to survive or implant in the uterus.
More Information:
Reviewed by health care specialists at UCSF Medical Center.
Last updated May 8, 2007
This information is for educational purposes only and is not intended to replace the advice of your doctor or health care provider. We encourage you to discuss with your doctor any questions or concerns you may have.
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