IVF Risks Mostly Due to Multiple Births
Single-Embryo Transfer May Cut Risk of in Vitro Fertilization
Single-Embryo Transfer: Answer to IVF Risk?
In the U.S., doctors typically implant two or more embryos, which greatly increases the chance of multiple births -- and greatly increases pregnancy risk.
"The majority of the patients want three or four embryos to be transferred," Attia says. "In the U.S., there is a different mentality. Most of this is not covered by insurance, so they really want to get pregnant on the first try and not have to do this several times. In Europe, where IVF is mostly covered by national health services, there is much more stress on single-embryo transfer."
Sutcliffe says that European doctors achieve nearly the same success rate with single-embryo transfers as with multiple-embryo transfers. Given the vastly reduced risk of multiple births, he suggests that U.S. doctors should look to Europe for guidance.
"My research, and that of many others in the field, suggests that if IVF babies are not born prematurely, they really have virtually the same prospects as a naturally conceived child," Sutcliffe says. "Especially in the U.S., the main risk is due to the fact that people are putting in too many embryos. As a result, you can have twins, triplets, quadruplets, or more and expose yourself and your babies to the risk of premature birth."
"Definitely single-embryo transfer is much better," Reddy says. "The problem is that for older women, you have to balance out the cost and the number of procedures. For a woman over 40, it is gong to take many more cycles. But we in the U.S. are trying to increase the amount of single-embryo transfers and decrease the number of multiple-embryo transfers."
Indeed, the American Society for Reproductive Medicine's June 2006 guidelines suggest that doctors transfer only a single embryo for women under age 35 with good prospects for success. For women under age 38, they recommend transfer of no more than two embryos. But for older women or women with poorer prospects for successful pregnancy, the ASRM leaves the door open for transfer of up to five embryos.
Attia says his institution does not transfer more than two embryos per procedure. He and Reddy each note that twin births do not appear to be as risky as higher-multiple births. Both join Sutcliffe in calling for more research.