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Surrogate Pregnancy after transfer of Cryoshipped, Vitrified Human Blastocysts

Rotunda achieved its first pregnancy with Cryoshipped Vitrified embryos from USA and transferring them into a surrogate mother.

Till now, we have received frozen embryos from many countries and successfully transferred them into surrogate mothers at Rotunda. Most of these embryos were frozen by the slow freezing process. As vitrification is becoming popular as a method of choice for freezing gametes, we have started receiving vitrified embryos from world over. Our first case of cryoshipped, vitrified blastocyst transfer has resulted in a pregnancy.

A short history lesson:

In 1972 preimplantation mammalian embryos were first successfully cryopreserved. The method was very time consuming. Slow cooling was used (1 degree/min or less) to about -80 degrees Centigrade. Then the embryos were placed in liquid nitrogen.

The embryos also needed to be thawed slowly and a cryoprotectant added and removed in many gradual steps. This was a lot of work.

The first reported pregnancy in humans from frozen embryos was in 1983.

Most of the research has been done on mouse embryos. Development of frozen thawed mouse embryos, in vitro and in vivo, is not statistically reduced as compared to their nonfrozen counterparts.

Research continues in this area and human embryo freezing and thawing protocols have improved tremendously over the past 25 years. Hopefully, the newer vitrification technique will prove to have equivalent success rates with human blastocyst embryos transferred fresh or after freezing and thawing.

What is the difference between slow freezing and vitrification?

Patients who undergo IVF may have several eggs collected. The eggs are then fertilized with a sperm and checked for fertilization. Fertilized eggs are called embryos. A patient may have multiple high quality embryos eligible for embryo transfer back to the uterus. A certain number of embryos are chosen for embryo transfer, and the surplus of high quality embryos can be cryopreserved for future use.

Previously, embryos were cryopreserved using a slow freeze method. Embryos were run through different solutions of media toStorage of Cryopreserved embryosdehydrate the cells of water and replace it with cryoprotectant. Then the cryoprotected embryos were individually labeled and stored in cryopreservation straws, which were put in special freezers. These freezers slowly (-0.3 degrees Celsius per minute), cooled the embryos to -35 degrees Celsius using liquid nitrogen. They were then stored in liquid nitrogen (-196 degrees Celsius). At that extremely cold temperature, cellular activity is essentially brought to a halt, allowing the embryos to remain viable indefinitely.

When patients decide to use their cryopreserved embryos to try for a pregnancy, the embryos are removed from the liquid nitrogen, warmed and run through solutions of media to remove the cryoprotectant and rehydrate the cells with water. During cryopreservation, the formation of intracellular ice crystals can damage the cells of the embryo, decreasing future viability. Therefore, new methods were developed to improve cryopreservation techniques.

vitrification-hook 1Recent technical advancement in the field of cryobiology has opened up various options for freezing gametes and embryos at different developmental stages. The tendency of the IVF world to switch over to natural cycle IVF and to elective single-embryo transfer has put cryotechnology in the forefront of IVF. Vitrification method is gaining popularity as the method of choice for gamete/embryo cryopreservation.

Vitrification is a new process for cryopreserving embryos. Through vitrification, the water molecules in an embryo are removed and replaced with a higher concentration of cryoprotectant than in the slow freeze method. The embryos are then plunged directly into liquid nitrogen. This drastic (-12,000 degrees Celsius per minute) freezing creates a glass transition temperature, commonly called a “glass” state, and the embryos are vitrified. This quick freezing reduces the chance for intercellular ice crystals to be formed, thus decreasing the degeneration of cells upon thawing for embryo transfer.

In 1998, it was shown that vitrification using an EG-based vitrification solution (EFS40) (Kasai et al., 1990) with conventional cryo-straws was effective for human embryos at the 4- to 8-cell stage (Mukaida et al., 1998). The effectiveness of vitrification was confirmed for human embryos at the 8- to 16-cell stage (Saito et al., 2000) and the morula stage (Yokota et al., 2001b), also using EG-based solutions.

Many studies show survival rates of vitrified embryos to be far higher than survival rates of slow freeze embryos. Thus far at Rotunda, vitrification results are very encouraging, and we are excited to offer this cutting edge technology to our patients.

For more information about vitrification, ask to speak to the embryologist at your center.

Vitrification, a cutting edge technology for cryopreservation of embryos, is now available at Rotunda – Center for Human Reproduction.


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Céline Dion Pregnant with Embryo Frozen for Eight Years

As wake-up calls go, this one was hard to beat. Thérèse Dion was asleep in her room at the five-star Hotel Le Bristol in Paris, where she had gone to film episodes of the cooking show she hosts on Canadian TV, when the phone rang at 7 a.m. on Jan. 25. On the line, more than 4,500 miles away at Palms West Hospital in Loxahatchee, Fla., the youngest of her 14 children, pop diva Celine Dion, was 18 hours into labor and literally seconds from giving birth. “I heard the baby’s first cry live on the telephone,” says an elated Thérèse, 73, who spoke to her daughter only briefly. “Celine told me, ‘The baby is in good health, but the mother, she is tired.'”

As well she might have been. After years of publicly wishing for a child—and enduring an intensive round of in vitro fertilization treatments to conceive—Dion, 32, and her husband-manager, René Angélil, 59, finally welcomed 6-lb. 8-oz. René-Charles three weeks before his Valentine’s Day due date.

“Everybody was just crying tears of joy,” says Dion’s obstetrician Dr. Ronald Ackerman, 48, who assisted in the cesarean section delivery performed by his partner Dr. Steven Pliskow, 37. “Nurses, doctors, experienced people—there was not a dry eye in the room.” Least of all those of the proud parents (who declined to release pictures of the newborn). “This was their dream,” says record producer David Foster, a longtime friend. “It’s bigger than any hit record, bigger than anything for them.”

Dion had been relaxing at the couple’s 10-bedroom mansion in nearby Jupiter when contractions began on Wednesday afternoon. After consulting Ackerman, the singer and her husband packed their black Mercedes 500 and drove to the hospital 40 minutes away. But the baby for whom they had waited so long wasn’t ready to take the stage just yet. At one point Ackerman and Pliskow tried to induce the birth chemically, to no avail. “They gave it every chance to be a vaginal delivery,” says maternity nurse Helene Schilian, who cared for Dion during her three-day hospital stay. “But at some point the baby just seemed to say, ‘I’m tired, let me out.'” By 1 a.m. Thursday (up to 24 hours of labor is not unusual for a first-time birth), the doctors became concerned that the umbilical cord was in a position to damage the child and performed a cesarean section.

Throughout the birth Dion was “focused and calm,” says Ackerman. “This is a lady with extreme focus and fortitude,” adds Pliskow. After Angélil helped cut the cord, René-Charles was placed in his tearful mother’s arms before being washed and wrapped in a hospital-issue blue-and-pink-striped blanket, topped with a knitted cap. Then Angélil and Dion’s sister Linda, 41, who had also attended the birth, began the task of spreading the news. “The baby of the family had a baby!” sister Liette, 50, who lives in Montreal, exclaimed when she heard of the birth. “We were that much more excited because she so wanted to have a baby and the way she became pregnant was a miracle in itself.”

The next morning Dion made some phone calls of her own (“I had a boy!” she announced to Manhattan fertility specialist Dr. Zev Rosenwaks, who had administered her IVF treatment back in May) and made a careful inventory of her new baby’s features. “He has René’s little feet, René’s toes and the little ears of René,” she told her mother over the phone. “He has my chin, though, and my hair color.” Over the next couple of days the songstress never left her birthing suite, a green-and-peach-hued room with a bathroom, dining table and two foldout beds that Angélil and Linda occupied at night. Dion cooed softly to the baby in French (“Mon amour”) and approached her mothering with the singular determination that earned her five Grammys and more than 100 million worldwide album sales in her singing career. “She took to nursing the baby like she’d had 12 others,” says Schilian. “She handled that baby like a pro.”

For his part, “René was very attentive,” Schilian adds. “He was up for every feeding during the night, making sure the baby got fed every three hours. He changed diapers.” Whenever he did step out, the new father couldn’t conceal his joy. After munching on a chili hot dog at the nearby Chicago Style Grille on Thursday, Angélil returned the next day with a signed photograph of his wife for the deli’s owner Scott Verdung. At breakfast on Saturday at a local diner he tipped waitress Erla Simon, 18, $20 on a $20 check—”The biggest tip I ever got!” she says. And staff at the nearby Babies R Us were struck with Angéli’s happiness when he stopped by that same day for a bottle sterilizer, a nursing pillow and a baby car seat, which store clerk Mike Maldonado helped him install in his Mercedes. “You could tell he was a little nervous,” says Maldonado, “a little anxious about making sure it was done right.”

Maybe so. But when it comes to raising children, both Dion and Angélil have had plenty of practice. Dion dotes on her 32 nephews and nieces—for whom she bankrolls annual Christmas toy shopping free-for-alls—as well as the children of friends. “Even when a baby is crying or upset, as soon as she takes them in her arms they become quiet and happy,” says her pal and Canadian press agent Francine Chaloult. “She knows how to hold a baby, cradle a baby, feed a baby, handle a baby.” So does Angélil, who had his share of diaper duty while raising his three other children—Patrick, 33, Jean-Pierre, 26, and Anne-Marie, 23—from two prior marriages. “If you want to know what kind of a parent René is, look at those children,” says David Foster. “They’re polite, nice, successful.”

Their father had been divorced for three years when he and Dion, whose career he had nurtured since she was just 12, revealed their love to each other in 1988. Four years would pass before they admitted their relationship to the world. But there was nothing secretive about their 1994 wedding, a lavish affair with 500 guests at Montreal’s Notre Dame Basilica. (Five years later the pair renewed their vows in an equally opulent Arab-themed ceremony, complete with live camels and belly dancers, in Las Vegas.) From the start, having children was a priority. “I never thought that my life would fall apart if I didn’t have a child,” Dion wrote in her book My Story, My Dream, published last October. “But even so, I was waiting for it, looking for it and making it part of my plans.”

What the couple hadn’t planned on was the need for artificial conception. In the spring of 1999 Angélil was diagnosed with squamous cell carcinoma on a lymph gland in his neck. Concerned about the potential side effects of the chemotherapy and radiation he would require, the couple froze some of his sperm for future use. Tests before freezing found that Angélil’s sperm count was already too low for standard IVF treatments to be successful. So Dr. Ackerman suggested a procedure known as intracytoplasmic sperm injection—using a single, isolated sperm cell to fertilize an egg, which is then placed in the uterus. For a time the couple focused their energy on Angélil’s cancer treatment; they had already announced that beginning in 2000 Dion would take at least a year off from performing to “chill out and a discover new things,” as she put it—including starting a family.

Then, last February, the couple met with fertility specialist Rosenwaks. Four months later, after undergoing a battery of drug treatments and invasive, sometimes painful procedures, Dion received the happy news. “Congratulations, lovers,” Rosenwaks told them over the phone from Manhattan while Ackerman was by their side at their home. “You’re pregnant, Celine.”

Earlier that day the couple had learned that after some 38 rounds of chemotherapy and radiation, Angélil’s cancer had been cured. Overjoyed and eager to preempt tabloid reports, they shared the news of Dion’s pregnancy with her fans the very next morning: “There’s no hiding happiness,” they said in a statement. “We can’t keep something so big, so wonderful a secret just for us.”

Despite René-Charles’s extraordinary history, Dion enjoyed “a very normal pregnancy,” says obstetrician Pliskow. She followed a balanced diet, took prenatal vitamins, did water exercises, attended Spanish classes and read up on pregnancy and motherhood. “I’m basically now just a slob on the sofa,” she told David Foster over the phone one day. “That’s my life.” Still, she was as much the perfectionist in pregnancy as she was in her performing career. “She went above what she needed to do,” says her hairstylist Sheila Stott. “If the doctor said, you need rest, she’d go to bed for three days.”

Which, if you’re Celine Dion, is a long time away from the mall. On doctors orders, she-of-the-thousand-shoes stopped playing golf (she has an 11 handicap) and singing, but no one said anything about her other passion: shopping. At the upmarket stores near her Florida home, Dion stocked up on baby linens in white with gold trim at the Purple Turtle and visited Ralph Lauren, Saks Fifth Avenue, Charles David and Valentino, where sales assistants were impressed by the slim 5’7″ star’s maternity chic: clingy dresses (she gained just 25 lbs. during her pregnancy) with high heels and oversize sunglasses. At the Palm Beach outlet of the French baby-boutique chain Bonpoint-where infant sweaters sell for about $50—Dion “bought the entire autumn-winter 2000 collection and a few pieces from the spring-summer 2001,” reports store spokesman Vincent Debear. “In all, about 200 pieces.”

Celine and René, who divide their time between Florida and Canada, have already decorated the Florida nursery in white and blue, with a French provincial bassinet, a Burberry baby carriage (worth $4,250) and a wardrobe stocked with everything from blue-and-white onesies to baby golf shoes. But there was even more baby booty to be had at a surprise shower thrown by René’s daughter Anne-Marie and close friend Mia Dumont at Donald Trump’s Palm Beach club Mar-a-Lago on Jan. 3. The 90 guests—including many members of Dion’s family, whom Angélil had flown in for the event—all hid in a darkened room and when Celine entered yelled, “Surprise!” “Celine doesn’t really like surprises, but she was very happy,” says her friend Coco Lacroix. Later the couple opened gifts—including a handmade teddy bear from Thérèse, stuffed with heat beads, which had her daughter in tears. “This baby,” says Lacroix, “is the most lucky child in the world.”

Indeed, the media in Dion’s home province of Quebec has already dubbed René-Charles “Le Petit Prince.” And there’s little doubt he’ll be treated as such when Dion takes him home to be doted upon by grandmama Thérèse and grandpapa Adhémar, 77, a former butcher, and the infant’s 13 aunts and uncles. The trip, which she hopes to make in June, may turn out to be more restful than she imagines. “She won’t be seeing much of her little boy,” notes sister Liette. “Everyone will want to hold him!” Before then Thérèse plans to spend time in Florida helping her daughter; sister Linda has already been chosen to be the baby’s godmother. As for the future, only one thing is certain: Dion is in no hurry to resume her career. “I suspect that by 2002 she’ll be back to work in some form,” says Foster. “But that first year with her child is extremely important to her.”

Friends also suspect that René-Charles won’t stay an only child for long. Doctors say there is no reason the star couldn’t become pregnant again. And conveniently, a second embryo, frozen during her IVF procedure, lies stored at Rosenwaks’s Manhattan fertility clinic. “I will go get it,” Dion said an interview in December with Canada’s French-language TVA television station. “That’s for sure.” Maybe in the near future: As she left Palms West Hospital on Jan. 27, 2001 Dion bade a fond farewell to the staff of the maternity wing, then added breezily, “See you next year!”

Céline Dion, now expecting her second child, is “very excited,” says her doctor, Dr. Zev Rosenwaks, who performed the in vitro fertilization procedure that made the 41-year-old singer’s pregnancy possible. When he called her earlier this week to say the pregnancy test was positive, “You could hear her chuckling,” he says. “She was very happy. So was René. They are both very thankful.”

Rosenwaks, director of the Ronald O. Perelman and Claudia Cohen Center for Reproductive Medicine at New York-Presbyerian Hospital/Weill Cornell Center Medical Center, implanted a embryo that had been kept frozen in liquid nitrogen for the past eight years. “She is very, very early in her pregnancy,” says her doc.

Dion had her embryos frozen when she went through IVF while trying to conceive her first child, René-Charles, who was born in 2001. When she completed her performance run in Las Vegas in 2007, she consulted Rosenwaks about trying again. “She came back to have the embryos transferred back because she wanted to have another baby,” he says.

According to the fertility specialist, freezing an embryo for eight years is not necessarily a problem. “There have been embryos that have been [frozen] for more than 10 years, and even more than 15 years, that have successfully thawed and resulted in a pregnancy,” says Rosenwaks.

Meanwhile, the doctor says, “She is feeling well. So far, so good. I look forward to hearing the fetal heartbeat. René and Céline are both looking forward to a pregnancy that is a healthy one.” He adds, “There is no question she is ecstatic.” Picture 1


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First the Biopsy, then The Baby

picture-42picture-32A common medical procedure may be the key to helping couples who’ve had no luck with artificial insemination and IVF. Could a common uterine biopsy make pregnancy “stick” for women having trouble conceiving? A small but growing number of couples are embracing an unusual use of biopsies during infertility treatments in the belief that they may help increase the chances of a successful pregnancy. In a handful of small studies, biopsies of the endometrium, the lining of the uterus, which are usually performed as a diagnostic tool to sample tissue and test for infections, disease or other problems, have been found to boost the pregnancy rates of women who had tried in-vitro fertilization and failed to become pregnant. One Toronto couple credits the procedure with the first successful pregnancy in 10 years of trying. After 11 artificial inseminations and two IVFs proved fruitless, Roslyn and Howard Kaman had experienced the gamut of failure, from miscarriages to ectopic pregnancies. They had opted to try adoption when they read an article about a lecture at Toronto’s Weizmann Science Canada by an Israeli researcher, Nava Dekel. In 2003, Dr. Dekel found that 45 women who had undergone a uterine biopsy during the menstrual cycle before undergoing IVF had almost twice the rate of pregnancies and births compared with a control group of 89 women. In 27.7 per cent of the women in the biopsy group, the embryo transfer was successful. The IVF worked for just 14.2 per cent of the control group. The Kamans wrote to Dr. Dekel, and she connected them with the fertility clinic in Israel that had performed the procedures. Doctors there sent the couple a detailed protocol, which involved three separate biopsies on particular days in the cycle just before an IVF treatment. The Kamans’ Toronto fertility specialist, Fay Weisberg, agreed to try it. Ms. Kaman became pregnant on the first IVF cycle after the procedure and baby Hannah is now three months old. “I still can’t believe it. I think I will go through my whole life and not believe we were successful,” says Ms. Kaman, 41. While broader research is being conducted to confirm the role these biopsies may be playing, anecdotal evidence is starting to mount suggesting that the disruption of the uterus somehow leads to the successful implantation of an embryo. Some practitioners say they’ll wait for randomized trial results before they start offering biopsies to IVF patients. Togas Tulandi, a McGill University medical researcher, is hoping to figure out what role the biopsies might play, if any, in the successful pregnancies of women like Ms. Kaman. He is in the midst of conducting a large randomized study (he hasn’t yet reached his goal of 162 participants) and says that if the biopsies are working, the mechanism may be akin to tilling the soil before you plant a tulip bulb. “Maybe this slight injury to the endometrium makes the environment for implantation better,” he says. “If we can prove that it works, we can do it routinely.” Since the procedure carries little risk, other than discomfort and a very small chance of infection or injury to the uterus, many fertility doctors are already incorporating it into their practices. While it is not listed on her menu of services at the First Steps Fertility clinic where she is medical partner, Dr. Weisberg says she now offers it to most of her patients who have failed to conceive with IVF and for most patients before they undergo a frozen embryo transfer. “I suspect that it will probably soon be a routine for all patients undergoing IVF.” The only reason it’s not routine is a paucity of large studies and the fact that it’s painful and uncomfortable for most women, she says. Although she can’t unequivocally say whether the biopsies are effective – “the women end up being their own control” – Dr. Weisberg has a hunch that they work. It could have something to do with increased blood flow, or the way in which the proteins in the uterus heal, she says. “I do believe something changes deep down.” And she’s not worried about a stampede for the procedure on the part of desperate couples. “Not to be cavalier, but this is a procedure already being done on younger women for bleeding of the uterus and other problems,” she says. “It’s easy, quick, but painful. There’s no anesthetic. You can go right back to work.” Other specialists take a more cautious approach. Fertility expert Arthur Leader does not offer it to patients at the Ottawa Fertility Centre where he practises. Until a randomized study such as Dr. Tulandi’s can prove that women undergoing these biopsies have a better chance of getting and staying pregnant, “the precautionary principle should apply,” he says. “You shouldn’t do it until a benefit has been shown.” He points out that there have been many other treatments, including low-dose Aspirin, a blood protein called albumin and a diabetes drug called metformin, that were believed to help women conceive and were routinely prescribed but which, after much study, proved either to do harm or have no effect. And, as far as Dr. Leader is concerned, “No good is harm.” For couples who end up with a healthy pregnancy after uterine biopsies, it’s hard not to credit the procedure for their little bundles of joy. Still, Ms. Kaman says that even though she suspects the treatment did work, there may have been some luck involved. When she imagines trying for a second IVF baby, “part of me thinks lightning’s not going to strike twice with us.” Anatomy of a biopsy An endometrial biopsy is performed by inserting a suction catheter through the vagina and cervix, into the uterus. The end is pressed up against the uterine wall where it cuts away a small sample of the lining tissue. Because of any number of factors, an embryo may not be able to attach itself to the cells that make up the lining of the uterus. After the biopsy is taken, some researchers and fertility experts believe that the slight damage caused to the wall of the uterus makes it a better environment for implantation, whether because of increased blood flow, the healing process or some other factor.

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Fate of surplus frozen embryos : a difficult decision

Many infertility patients with unused frozen embryos are dissatisfied with the common options offered to them, such as donating to another couple or discarding the embryos, according to a study to be published Thursday in Fertility and Sterility, the New York Times reports. It is estimated that more than 400,000 embryos are frozen at clinics across the U.S., and many infertility patients grapple with the decision of what to do with embryos after they no longer want additional children, the Times reports.

 picture-25The study, which was conducted by researchers at Duke University Medical Center, involved a survey of more than 1,000 infertility patients at nine clinics (Grady, New York Times, 12/4). The survey found that donating embryos for research was the most popular option (Rubin, USA Today, 12/4). Among study participants who said they did not want any more children, 66% said they would be likely to donate their embryos for research, but only four of the nine clinics in the survey offered the option. Fifty-three percent of participants who wanted no additional children said they did not want to donate their unused embryos to other couples, mainly because they did not want their biological offspring to be raised by other people or have to address the possibility that their own children could encounter an unknown sibling in the future. In addition, 43% did not want their embryos discarded, and 20% said that their embryos likely would remain frozen indefinitely. Embryos can remain viable for 10 years or more if properly stored, although not all of them survive after thawing, the Times reports. According to the Times, a small number of study participants “wished for solutions that typically are not offered,” such as holding a ceremony during the thawing and disposal of the embryos or placing the embryos in the woman’s body at a time during her cycle when she was unlikely to become pregnant, so that they would “die naturally” (New York Times, 12/4).

 Lead author Anne Drapkin Lyerly — a bioethicist and associate professor of obstetrics and gynecology at Duke University — said a significant factor impeding embryo donation for research is the Bush administration’s 2001 restrictions on federal funding for research on new embryonic stem cell lines (USA Today, 12/4). Brigid Hogan, chair of the department of cell biology at Duke, said there is insufficient funding to fully research existing embryonic stem cell lines, leaving minimal use for the hundreds of thousands of embryos available. Hogan said, “Even if somebody said, ‘I’ve got 100 embryos I’m donating tomorrow,’ I think there are many places that would just say, ‘We don’t have the funding'” (Collins, Raleigh News and Observer, 12/4). Sean Tipton — a spokesperson for the American Society of Reproductive Medicine, which publishes Fertility and Sterility — said researchers are reluctant to accept embryos donated from other medical centers because of concerns about violating informed consent procedures. Lyerly added that the process of shipping frozen embryos also presents a challenge (USA Today, 12/4).

 Lyerly said, “The national debate presumes that if you care about and respect a human embryo, you would want that embryo to have a chance at life.” She added, “What we found was that people cared very much about what happened to their embryos, but one of their significant concerns was that their embryos not become children in families other than their own” (Collins, Denver Post, 12/3). Mark Sauer, director of the Center for Women’s Reproductive Care at Columbia University Medical Center, said choosing what to do with the leftover embryos is a “huge issue” for couples, adding that some patients ask to be given their leftover embryos, while others pay storage fees for years and years. The Times reports that some patients stop paying for storage and “disappear, leaving the clinic to decide whether to maintain the embryos for free or to get rid of them.” Sauer said patients who do that “would rather have you pull the trigger on the embryos. It’s like, ‘I don’t want another baby, but I don’t have it in me; I have too much guilt to tell you what to do, to have them discarded.'”

 According to Lyerly, many patients create as many embryos as possible to increase their chances of having a child. She added that more information needs to be given to patients early in the in vitro fertilization process to inform them of their options for unused embryos and letting them know that deciding what to do “may be difficult in ways you don’t anticipate.” She said that discussion about the embryos should be “revisited and not happen just at the time of embryo freezing, because people’s goals and their way of thinking about embryos change as time passes and they go through infertility treatment” (New York Times, 12/4).


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The Frozen Embryo Transfer

Frozen Embryo Transfer (FET)

If you have recently gone through infertility treatments or if you are considering undertaking IVF, you may be wondering what will happen to any extra embryos that are created during the procedure. If you and your partner have extra embryos that are not used during initial IVF procedures, these embryos can be frozen and then transferred to your uterus at a later date. Known as frozen embryo transfer (FET), this procedure has helped many couples facing infertility achieve pregnancy.

What is Frozen Embryo Transfer?
This procedure takes embryos that have been frozen for a period of time and replaces them into your uterus after they have been thawed. FET is a relatively non-invasive procedure, which is why many couples choose to have it performed. It can be successfully performed on women who are experiencing either natural or controlled menstrual cycles.Why Choose Frozen Embryo Transfer?
Many couples choose to have FET performed if they have had extra embryos remaining from an initial IVF cycle. Some couples do not like the idea of destroying embryos simply because they are “left over” from an IVF cycle. Other couples know or suspect that they will need to do IVF again in the future and prefer to freeze their embryos in order to make future IVF cycles less stressful physically for the female. 

In order to perform IVF, numerous embryos are created in order to ensure that healthy and viable embryos are available for transfer. Many couples decide to freeze some of these embryos in order to allow them the opportunity to get pregnant again in the future or for use in a later IVF cycle. 

Embryo Freezing
The FET procedure involves having your embryos frozen, or cryopreserved. The freezing procedure is as follows:


  • Your embryos are placed inside of special glass vials, that look much like straws.
  • These embryos are then mixed with a special solution, called cryoprotectant. This cryoprotectant prevents ice from forming in between the cells of your embryo.
  • The glass vials containing the embryos are then inserted into a controlled freezer filled with liquid nitrogen.
  •  They are cooled slowly until they reach a final temperature of -196° C.


Embryo Thawing
Before FET can take place, your embryos must be thawed after the freezing process. When your reproductive endocrinologist decides it is time to begin the FET procedure, your embryos will be removed from the freezer and thawed.


  • The embryos are allowed to thaw naturally, until they come to room temperature.
  • The embryos are then steeped in four separate solutions to help remove any cryoprotectant used during the freezing process.
  •  Your embryos are then warmed to body temperature (37°C) and mixed with a small amount of culture medium.

The Frozen Embryo Transfer Procedure

The FET procedure is actually fairly straightforward. 

Before Embryo Transfer
Before your embryos can be thawed and transferred, you and your reproductive endocrinologist need to decide how many embryos to transfer into your uterus. The number of embryos transferred will directly impact the success rate of the FET procedure. Typically, between three and four embryos are transferred during each FET procedure.

Your health care provider will then monitor your body in order to determine the best time for the embryo transfer. We usually give oral estradiol tablets to prepare the uterine lining. The thickness is measured on ultrasound scan. Your embryos will be thawed the day before your FET procedure.

The Transfer
The actual transfer of the frozen embryos is painless and straightforward, and only takes about 15 minutes.


  • A catheter is inserted through your cervix and into your uterus.
  • The embryos are injected into the catheter and deposited in your uterus.


After the Transfer
After the transfer your reproductive endocrinologist will likely have you continue any fertility medications that you may be using. Twelve days after the FET procedure, you will return to your clinic for a pregnancy test. 

Success Rates of Frozen Embryo Transfer

The success rates of FET really depends upon a variety of factors, particularly maternal age and the number of embryos transferred. Typical success rates are around 20% per cycle. It is important to know that not all embryos will survive the freezing and thawing process though. About 70% of embryos survive cryopreservation, and this can sometimes impact the success rates of FET. This makes it important to freeze and thaw a number of embryos when performing the FET procedure.

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