Sept. 14, 2005 -- Fewer than two in 10 embryos transferred during infertility treatments result in live births. But researchers say this success rate could be improved with better pretransfer testing that helps identify viable embryos.
Assisted reproduction most often involves the fertilization of eggs that have been surgically removed from a woman's ovaries. The fertilized egg, or embryo, is then transferred back into the patient in hopes of achieving a pregnancy.
Since 1995, reproductive clinics in the U.S. have been reporting their infertility treatment results to the CDC and the nation's top assisted-reproduction organizations.
A review of the data from 1995 until 2001 revealed that just 15% of embryo transfers in 2001 led to births.
That is an improvement over 1995, when just 10% of embryo transfers resulted in live births. But researcher Pasquale Patrizio, MD, says the pace of progress is too slow.
"With the techniques we have available right now to help us identify better embryos for transfer, we could definitely improve on that 15%," Patrizio tells WebMD.
The success rate for most infertility clinics these days is about 35%, meaning that about one in three assisted-reproduction procedures result in a baby. For every 100 couples treated, an average of 300 embryos will be transferred and 35 children will be born.
While this figure sounds low, a leading expert in infertility treatment points out that most egg fertilizations do not lead to live births, whether fertilization occurs naturally or with medical assistance.
"Humans are very inefficient when it comes to reproduction," American Society for Reproductive Medicine (ASRM) President Robert Schenken, MD, says in a news release.
"It can take millions of sperm cells, thousands of eggs, and dozens of embryos to produce one baby. We need more research to help us better understand the human reproductive process."
Fewer Embryos Transferred
Patrizio notes that doctors who treat infertile couples are under increasing pressure to transfer fewer embryos in an effort to reduce multiple births.
The average number of embryos transferred during a single in vitro fertilization (IVF) procedure declined from four in 1985 to three in 2001.
In guidelines announced late last year, ASRM and the Society for Assisted Reproductive Technology called for no more than two embryos to be transferred during a single assisted- reproduction procedure in women under the age of 35 who have a reasonably good chance of having a successful pregnancy.
But Patrizio says the goal of keeping the birth rate steady while transferring fewer embryos is unrealistic unless better methods of identifying viable embryos prior to transplantation are identified.
Wider use of pre-implantation genetic screening may help, he says, but the benefits of such screening have not been proven in rigorous clinical trials.
Embryo quality decreases as women age, and infertility treatment outcomes among patients in their late 30s and early 40s are even poorer than those reported in the study.
"Women who want to have children but are postponing reproduction need to understand that they shouldn't wait too long," Patrizio says.