THURSDAY, June 1, 2006 (HealthDay News) -- Transferring only one embryo during in vitro fertilization is as successful in older women as it is in younger women, a new Finnish study finds.
This raises the possibility that single-embryo transfers could become more common for women aged 36 to 39, reducing the likelihood of multiple births and the accompanying health risks.
"We weren't sure if the quality of the embryo made that much of a difference ... We didn't have a clear-cut study demonstrating that," said Dr. Abe Shahim, an obstetrician/gynecologist with Lenox Hill Hospital in New York City. "This study really does that. If you have a good embryo, no matter what the age of the mother, you still are getting very good results."
The finding appears in the June 1 issue of Human Reproduction.
The norm in IVF treatment is to transfer more than one embryo to the womb, thus increasing the chances of a live birth. This, however, results in a higher likelihood of having multiple births, which can lead to increased complications to both baby and mother.
Single-embryo transfer in Finland has resulted in an overall multiple pregnancy rate of less than 10 percent in many clinics. "That is fantastic for IVF," Shahim said.
The authors wanted to see if the overall multiple pregnancy rate could be lowered even further by employing the practice in older women, aged 36 to 39.
To that end, they analyzed 1,224 in vitro fertilization (IVF) cycles and 828 frozen embryo transfers in women in their late 30s.
The 1,224 IVF cycles included 335 elective single top-quality embryos, 110 elective single non-top-quality embryos, 194 compulsory single embryos (when there was only one embryo available) and 585 double-embryo transfers. The authors also analyzed the results for women who underwent more than one cycle using fresh and frozen embryos.
One-third of the women in this study became pregnant after one cycle of elective single-embryo transfer, compared to 31 percent to 35 percent of younger women in previous studies. The live birth rate in the older group was also comparable: 26 percent, vs. 27 percent to 30 percent in the younger set.
The cumulative pregnancy rate for the older women after using frozen embryo transfer was 54 percent, with a live birth rate of more than 40 percent. In young women, that number was higher -- 60 percent to 70 percent -- although, the authors stated, the 40 percent rate is still satisfactory.
Finland, Sweden, Belgium and the Netherlands routinely use single-embryo transfers, unless there are contraindications. Sweden has legislation which allows transfers of two embryos only in certain cases. In most countries, the standard is to transfer two embryos in women over the age of 36, the authors stated.
"Single-embryo transfer is not commonly done in the U.S. because, in general, most of these cycles are paid for by the patients," Shahim explained. "They're looking for the highest success rate on each cycle."
For that reason, Shahim expressed doubt that single-embryo transfer would take off in this country.
And there are still some research issues. "One of the concerns we have with older patients is they don't have as many good embryos," Shahim said. "I think that is the bigger issue. If they have a very good embryo, then fantastic, we've hit the nail on the head. But what if you weren't getting that very good embryo?"
Shahim said he would also like to see studies done in women aged 40 and over.
"As pure science, this is fantastic that we know that if you have a good embryo, you're very likely to get a good result," he said. "If not, you're still in the same boat. We need to do more research on the likelihood of getting good embryos in an older population."
Visit the Society for Assisted Reproductive Technology for more on IVF and other assisted reproductive techniques.