May 31, 2006 – When it comes to assisted reproduction, embryo quality rather than a woman's age should determine whether one or two embryos are transferred, new research suggests.
Researchers in Finland report that infertile women between the ages of 36 and 39 with good quality embryos had just as much success in conceiving when a single embryo was transferred following in vitro fertilization (IVF) as younger women.
In the U.S. and many other countries, the transfer of two embryos is the norm in women over the age of 35 to maximize the chances of achieving a successful pregnancypregnancy. But the practice dramatically increases the risk of twin births, which are far more risky than single-delivery births.
40% Delivered Babies
The Finnish study included only women older than 35 and younger than 40 who received either elective single embryo transfers with good quality or poorer quality embryos or double embryo transfers.
About a third of the women achieved a pregnancy with single embryo transfer using a high-quality embryo and a quarter had a live birth after just one try. These figures are comparable to those seen in earlier studies of younger women.
When more than one attempt with single embryo transfer was made using frozen embryos, 40% of the older women in the study with good quality embryos ended up delivering a baby.
The twin birth rate in women who got elective single embryo transfers was just 2%, compared with nearly 17% in the double embryo transfer group. The study is published in the June issue of the journal Human Reproduction.
"As well as elective selective embryo transfer having the potential to be as successful in women up to 40 as it is in younger women, it also reduces the risk of multiple births compared with double embryo transfer and therefore increases the safety of assisted reproduction in this age group," senior researcher Hannu Martikainen, MD, noted.
It's Different in the U.S.
Assisted reproduction specialist David Adamson, MD, FRCSC, agrees that embryo quality is more important than a woman's age in determining whether she should have a single or double embryo transfer when undergoing assisted reproduction.
But he adds that very significant differences in the U.S. and Finnish population of women undergoing IVF and embryo transfer make comparisons between the two groups difficult.
Adamson is vice president of the American Society for Reproductive Medicine. He is in private practice in Palo Alto, Calif.
IVF can cost anywhere from $10,000 to $15,000 in the U.S., and the patient typically pays the tab. In Finland and other Scandinavian countries, assisted reproduction is free to the patient.
American women usually try cheaper infertility treatments before they move on to IVF, while women in Finland are more likely to be offered IVF from the start. Because of this, American women tend to be older when they first have IVF and they may have more severe infertility.
Adamson points out that roughly five times as many women in Finland have IVF as in America.
"It is easy to see that if five times as many women are doing this, many of them have less severe infertility," Adamson says. "They have not failed other therapies like many women in the U.S."
He adds that the women in the study were highly selected, with only 27% considered to be good candidates for single embryo transfer. Almost three-quarters of the women in the study were not considered good candidates because the embryos available for transfer were of poorer quality.
Adamson says it is clear that there are still too many multiple births occurring with assisted reproduction in the United States, but he says progress has been made.
The transfer of three and even more embryos was common just a few years ago, but it is rare today unless the embryos are of very poor quality. As a result assisted reproduction-related triplet births were reduced by half between the late 1990s and 2003.
Reproductive endocrinologists in the U.S. are increasingly recommending single embryo transfer to their patients with good-quality embryos, Adamson says. But more often than not, patients reject the idea because they are more concerned about IVF failure than having twins.
"Multiple births are an important problem, but we must not forget that the purpose of assisted reproduction is to get a baby," Adamson says. "The only way to ensure no multiples is to have no live births at all."