At Shady Grove Fertility, an exciting new development in embryo cryopreservation, or embryo freezing, is helping more and more families achieve success. Frozen Embryo Transfer, or FET, used to be considered the less talented understudy to In Vitro Fertilization (IVF) – if your embryos survived freezing and thawing, you had a chance of getting pregnant, but not the kind of chance you would have with another fresh cycle of IVF. Now, all that has changed, and FET is the rising star of fertility treatment.
In the last few years, new techniques for freezing and storing embryos have provided a huge leap forward in Shady Grove Fertility’s success rates with FET, nearly matching the success of fresh IVF cycles. This increased success means patients have a second chance at pregnancy that is equal to the first, without going through the complicated steps and expense of a new IVF cycle.
As word has spread about the increasing success of FET, Shady Grove Fertility patients have opted more and more to use FET. In fact, we’ve already performed 800 of these cycles this year. This means more patients are become parents – one healthy baby at a time.
What is a Frozen Embryo Transfer?
Embryo freezing or cryopreservation is used when a patient undergoing IVF produces more high quality embryos than she wants to transfer during a cycle. Those “extra” embryos are then frozen and stored in the lab for future use.
When the patient decides she wants to use her frozen embryos, a pre-cycle ultrasound is performed to ensure there are no cysts or other structural problems within the reproductive system. Then, medications are given to optimize the lining of her uterus for implantation.
The total amount of medication is far less than that given in a fresh IVF cycle. Estrogen and progesterone injections are given every third day for up to two to three weeks. Then, the uterine lining is checked once more by ultrasound before the transfer. Not only do FET cycles avoid the frequent ultrasound and bloodwork required of an IVF cycle, they also don’t require the most trying aspect of IVF, the egg retrieval.
After this two-plus week preparation, the frozen embryos are thawed and transferred. A blood test to determine pregnancy is performed 14 days later.
Increasing Success Gives Patients Confidence in FET
“It used to be that when we used frozen embryos, the pregnancy rate was less favorable than when we used ‘fresh’ embryos from an IVF cycle,” said Dr. Levens. “Now, those rates of success for frozen embryos are just about equal to the rate of success of using fresh embryos, which opens up a whole new world of possibilities for patients.”
With more, and healthier, embryos being produced for FET cycles, the number of clinical pregnancies per embryo transfers with frozen embryos, according to Shady Grove Fertility’s IVF Statistics, rose to 49% in 2010. This number is identical to the pregnancy rate achieved with “fresh” embryos over the same period of time.
Dr. Levens says, “Patients used to worry that if they didn’t transfer all the good embryos created during an IVF cycle, they would be reducing their chances for pregnancy. That’s why the FET success rate is so important. It shows patients that they can transfer fewer embryos per cycle and still have the same chances of getting pregnant.”
Because of this increased success, Shady Grove Fertility has been doing more and more FET cycles every year. Jim Graham, Shady Grove Fertility’s Laboratories Director, says, “Last year, we did a little over 800 FET cycles. This year, we’ve already done that many and are on track to do about 1,200 cycles.”
Freezing embryos is an art form in reproductive medicine. Prior to freezing the embryo, our embryologists place it in a cryoprotectant, or anti-freeze solution, made out of sugar which replaces the water within the embryo’s cell with a concentrated solution. This solution helps protect the cells from the formation of damaging ice crystals.
In the traditional, slow freezing process, embryos would be exposed to multiple cryoprotectants, added in a specific order, over a 20 minute period. The cryoprotectant liquid would then be slowly cooled to -321 degrees Farenheit – the temperature of liquid nitrogen – until it was frozen. This two hours process was designed so that the cryoprotectants would infuse into the embryo’s cells and protect it from ice. While it has been, and still is widely used, this method of freezing often results in the loss or damage of embryos upon thawing.
In 2009, Shady Grove Fertility began using a new technique called vitrification. This process uses the same principles as the old method of freezing, namely replacing the water inside the embryo with cryoprotectant, but instead of a gradual freeze, the embryo is cooled rapidly which protects the embryo inside the liquid.
“In the final step of cryopreservation, the embryo is loaded onto a stick and plunged into liquid nitrogen,” Graham says. “Instead of freezing, it is supercooled so that the nitrogen becomes solid. This happens in about a minute. The embryo is then suspended in a glass-like bubble of the media.”
When the vitrified embryos are thawed, they look nearly identical to when they were fresh. “When they thaw, we assess them again. If they have damage that we think will reduce the chance of survival and implantation, these embryos are not considered viable for transfer and we move on to the next one,” Graham says. Because of this, patients can be assured that only the embryos with the best chance for producing a pregnancy are transferred.
With vitrification, the survival rate of embryos is about 95% and they have almost no loss of quality when thawed.
In this, as in all aspects of fertility treatment, the expertise and experience of the lab makes a big difference. Jim Graham says that because of the number of embryos Shady Grove Fertility’s lab sees in a year, its embryologists gain an expertise that many other labs can’t offer them.
“We understand the nuances and variabilities of different people’s embryos because of the volume of work we do,” he said. “What an embryologist in a smaller lab might see once in a career, we will see or two or three times in a year. That enables us to be much more confident in our decisions and to continually refine our techniques.”
The Benefits of FET
The most important thing for patients to know is that the use of frozen embryos is safe.
“With the FET success rate being what it is, patients can transfer one embryo and freeze the rest,” explains Dr. Levens. “If the first try doesn’t result in pregnancy, they have just as good a chance of getting pregnant with the frozen ones, using an FET cycle.”
He adds, “For patients who are under 37 and produce at least two high quality blastocysts, the rate of pregnancy is about the same whether they transfer one or two blastocysts. However, their chances of having twins are 43% higher if they transfer two.”
Jim Graham agrees, “Our goal in the lab is to help get multiple pregnancies as close to zero as possible, to reduce high-risk pregnancies. Improving the success rate for FET is the best way we can do that.”
Dr. Levens also points out to patients that, “time stops for your embryos when they are frozen. So, you can use those embryos to grow your family in the future without the worry of the increased risk that aging poses in terms of chromosomal abnormalities and miscarriage.”
Many patients at Shady Grove Fertility have used the frozen embryos from a single cycle of IVF to have their second and third child years apart without going through a new IVF cycle.
Will I Have Enough Embryos to Freeze?
“Sometimes patients ask me before a cycle, if they will be able to freeze embryos,” says Dr. Levens. “I tell them that I can’t predict what will happen. But, if they are under 35 and respond well to treatment, they have a good chance of having enough high-quality embryos that they will have some to freeze. Older patients, unfortunately, may not have enough to freeze.”
Shady Grove Fertility has strict standards for freezing, so only the highest-quality, day five or day six blastocysts are frozen. Jim Graham says, “Embryos have to pass a lot of milestones to be considered for cryopreservation. In addition, we look for factors that we know give an embryo the best chance of implanting, the most important of which is a good inner cell mass. The good news is that with vitrification, almost all of those good embryos preserved will survive the thawing process with little to no damage.”
Graham adds that about 40% of Shady Grove Fertility’s patients choose to freeze embryos. However, he believes that 50% of patients have embryos that are good enough to freeze, meaning that some patients, who could, choose not to freeze for financial or other reasons.
Cost Benefit of FET
“Cost is usually the main concern of my patients when we talk about freezing embryos, which is understandable,” says Dr. Levens. “That’s why I talk to them about FET right from the beginning. I want them to be able to look at the cost-benefit analysis for themselves and see that if they are lucky enough to have embryos to freeze, it’s definitely worth the cost.”
An FET cycle is less than half the cost of an IVF cycle even including the cost to cryopreserve and store the frozen embryos. Dr. Levens adds, “If you compare this to the cost of the complications that can be involved with twin pregnancies or even with having healthy twins, an FET cycle is much, much more cost-efficient.”
For patients using the Shared Risk or Multi-Cycle Discount Programs, Frozen Embryo Transfer cycles are like bonus cycles they get for free. Both programs allow for unlimited frozen cycles related to the fresh IVF cycles provided in those programs without counting toward program limits. For example, a patient can do a cycle of IVF and do two cycles of FET before being considered to have started cycle two of the six provided for in the Shared Risk Program.
The Bottom Line
FET is a win, win for patients Dr. Levens says. “It gives patients the same chances of success with much less risk and cost. I always tell them, if you are lucky enough to be able to freeze embryos, you should do it, because great things can happen.”