Single Embryo Transfer

With advances in fertility treatment, fertility clinics are not transferring as many embryos as in the past, and the use of single embryo transfer (SET) is becoming more common with In vitro fertilization (IVF). In SET, one embryo is selected and placed in the fallopian tube or uterus. The embryo could be a fresh embryo, a frozen embryo from a prior IVF cycle or a donor embryo.

"I think most programs in the U.S. and Canada, [have laboratory support with] a very good level of fluency with extended embryo cultures and testing embryos, so the best selections can be made to improve the chances that a single embryo transfer will result in a healthy singleton live birth," says E. Scott Sills, a fertility doctor with Pacific Reproductive Center in Irvine, CA.

Advances in embryo freezing have also reduced the need to transfer multiple embryos, according to Dr. Sills. "There’s really no urgency to transfer everything up front in the first cycle," he explains. "One embryo may be transferred fresh, maybe two depending on the age of the patient, and any non-transferred embryos can be frozen for possible use later."

Dr. Sills explains that the ability to transfer embryos at the blastocyst stage, as well as the ability to perform preimplantation genetic screening (PGS) with array comparative genomic hybridization (aCGH) to test for chromosome abnormalities, makes single embryo transfer a more satisfactory option for patients. "If only one embryo is transferred, then that decision must be based on a comprehensive chromosomal assessment," he says.

Recommendations for Single Embryo Transfer

In October 2011, the Practice Committees of the American Society for Reproductive Medicine (ASRM) and the Society for Assisted Reproductive Technology (SART) issued a report calling for an increase in the use of elective SET in good prognosis patients undergoing IVF. The committee had reviewed many studies that found single embryo transfer performed in a high quality laboratory is the best solution for patients who have a good prognosis, including:

• patients under age 35
• patients who have more than one high quality embryo available for transfer
• patients in their first or second IVF treatment cycle
• those with prior successful IVF cycles
• recipients of donor eggs

According to the 2009 Assisted Reproductive Technology report from the Centers for Disease Control, approximately half of the IVF procedures in the United States involved the transfer of two embryos, 23 percent involved three, and around 10 percent involved four or five embryos.

Two or More Embryos

In some patients, however, transferring two embryos may give them the best chance for a successful pregnancy and birth with IVF. A study published in the journal Lancet found that the odds ratios of live birth was higher in women aged 40 years or older than in those younger than 40 years when two embryos were transferred compared with one embryo. The study found that transferring more than two embryos did not help with success rates in women older than 30 and actually decreased success rates in women younger than 40.

"In modern practice, the safe option really is a one or two embryo transfer," says Dr. Sills. "Patients having a higher number of embryos transferred, three or more, that represents a very small minority of IVF patients in 2012. The mainstream approach would be to try to have a one or two embryo transfer."

Still, sometimes there is pressure to transfer more, and many patients still want to transfer more than one or two embryos.

Kathy Vaughn from Massachusetts, author of "My Journey Through Infertility - Battling Infertility, Dynasty Systems, and Old Yankee Healthcare," has been through nine IVF cycles, She says she and her husband tried pressuring their fertility doctor into transferring more embryos. "If not for changing IVF doctors and the transferring of more than three embryos, I would not be who I am today — the luckiest Mom in the world," she says, about having two successful IVF cycles. "We have two precious sons ages 6 and 4 who every day make our hearts smile because larger transfer batches of four and five embryos were performed given our history of IVF failures."

"We were certainly cognizant of, but not worried about, multiples or the risk that comes with multiples," she continues. "We, like many couples undergoing expensive fertility treatment, would have welcomed multiples. More bang for the buck, as they say! But more importantly, in coming from a large Irish Catholic family, being one of seven children myself, and knowing the love of a large family, multiples would have jumpstarted our family and brought us closer to the large family size my husband and I were so desiring of."