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Dr. Kim Mulvihill reporting New research raises questions about in vitro fertilization. Just how many embryos should a doctor put in a womb?
Many couples using in vitro fertilization are ending up with twins, triplets, or more. Some experts wonder whether there should be a limit to the numbers of embryos that are transferred.
It's been 26 years since Louise Joy Brown - the world's first 'test-tube' baby - was born in Great Britain.
Since then, an estimated one point two million children worldwide have been born as a result of in vitro fertilization -where eggs are harvested from a woman's ovaries, fertilized in a petri dish, and then placed in the uterus. Doctors initially transferred up to ten embryos, in hopes of getting just one live baby.
But as the science improved, so did the odds of success, and that often meant risky, complicated pregnancies with multiple fetuses.
Fertility specialist Dr. Carl Herbert says times have changed.
Carl Herbert/ Fertility Specialist: "Mostly by making better embryos. Better embryos come from better eggs. Better technology from the lab once you have better embryos you don't need so many."
But is transferring two or three embryos still too many? Maybe so, according to a new study.
Researchers from Sweden randomly divided women - age 35 and younger -- into two groups. Half the women had two embryos transferred, the others just one.
As reported in the New England Journal of Medicine, 39% of women in the single embryo group gave birth, compared to 43% when two embryos were transferred.
The real difference was in the rate of twins -- 33% in the double embryo group.
The greater the number of fetuses, the greater the risks. That's true even when you're talking about twins. Compared to a singleton pregnancy, twins are at higher risk of premature birth, low birth weight, cerebral palsy, and four times greater risk of death.
So is it time to limit the number of embryos to just one at time?
"Yes, I think it is critical that we decrease the number of multiple gestations that we create and the only way to do that is to reduce the number of embryoes we put back."
However,its not right for everyone. So if you set a law and say, one that's all you should have, there are a number of couple who will be badly influenced by the possibility of never becoming pregnant.
Now cost is also a factor. For many couples undergoing i-v-f, money plays a major role in decision making. It's expensive.
But you have to weigh the cost of how many i-v-f cycles you undergo, versus the medical costs of caring for premature or small babies who may have longterm health problems.