June 23, 2000 -- England, which gave the world the first 'test-tube baby' more than 20 years ago, now says that it's time to rein in fertility experts by limiting the number of fertilized eggs or embryos that are implanted into would-be mothers.
The limit comes in the form of a new fertility treatment guideline from the Royal College of Obstetricians and Gynaecologists, and the stated goal is to prevent unwanted triplets, quadruplets, and larger multiple births.
Mothers and babies both have greater risks during multiple births, according to a recent report in the CDC's Morbidity and Mortality Weekly Report. Mothers have a greater risk of excessive bleeding during and after delivery and a higher risk of needing a cesarean section -- a procedure that carries its own set of risks. Babies have a higher risk of lower birth weight, preterm delivery, and death. Other studies have shown that women carrying two or more babies are at increased risk of having high blood sugar and high blood pressure and that their babies are at increased risk for birth defects as a result of crowding and poor growth.
But at least one group of London-based fertility experts says the new guideline limiting implanted embryos to two could prevent some infertile couples from becoming parents, and leading U.S. experts agree.
Professor Ian Craft, MD, and colleagues from the London Gynaecology and Fertility Centre, make their case in a letter to the editor of the British Medical Journal. They write that the guideline is too broad. A better approach, they write, would be to develop a fertility index. The index should be based on a woman's risk of multiple pregnancy, and it could be developed so that those at high risk of carrying three or more babies could be implanted with one or two embryos, while those with low reproductive potential could receive "three or even more," they write.
They write that they have used a similar approach in their own clinic and have a very low rate of triplets even when they have implanted three embryos.
James M. Goldfarb, MD, MBA, director of in vitro fertilization, MacDonald Women's Hospital-University Hospitals of Cleveland, tells WebMD that he, too, thinks the U.K. limits are too restrictive. He says that the situation in the U.S. is very different than in the U.K. or Europe.
"In the first place, we don't have any legal requirements governing the number of embryos implanted," Goldfarb says. But he says that his center and others usually follow guidelines issued by the Society for Assisted Reproductive Technology .
"These general guidelines are based on age. If a patient is 30 or younger and has a good chance of becoming pregnant, the guidelines suggest a limit of two embryos," he says. "As you get towards age 35, the maximum becomes three, and then at 40, we would generally put back four."
But because the guidelines are "loose," each case can be evaluated individually, he says. "Sometimes we look at the embryos, and they are not growing as fast, don't look as likely to implant, so we might put back more," he says.
Sergio Oehninger, MD, professor of obstetrics and gynecology at the Eastern Virginia Medical School and director of the division of reproductive technology at the Jones Institute for Reproductive Medicine in Norfolk, agrees with Goldfarb about the need to consider each case separately.
He tells WebMD that the two embryo limit is "common in Europe. I think that is already the case in German and Sweden, and now the U.K. is taking the same approach." That approach may help explain why in vitro fertilization success rates in the U.S. tend to be better than the rates in Europe. "If you implant fewer embryos, the chances are that you will have fewer pregnancies," he says.
Oehninger says the limit on embryos is one element in an overall "softer approach to stimulation than we have in the U.S. -- where we take an aggressive approach to stimulating the ovary to produce more eggs that can then be fertilized to produce more embryos."
At the Jones Institute, which was the site of the first successful in vitro fertilization procedure in the U.S., Oehninger says there is now a shift toward "extending the culture of embryos from day 2 or 3 to day 5 so that we are actually transferring a blastocyst, or more mature embryo. This allows us to transfer only two and get a good success rate with very little risk of multiples." However, the blastocyst transfer is "not yet universally available," he says.
Even without blastocyst transfer, Goldfarb says the rate of triplet births associated with in vitro fertilization has decreased dramatically in the last 10 years.
"Today when we have a young patient, we implant two embryos and our success rate is better than 50%; 10 years ago we had to implant four embryos to get a 20% to 25% success rate. That more than doubled the chance of triplets. Now the [triplet] rate isn't zero, but it's less than 5%," says Goldfarb.
- Health officials in England are limiting the number of embryos that can be implanted in a woman for in vitro fertilization, in an effort to stem the number of multiple births.
- Experts argue that the new policy is too rigid, and the number of embryos to be implanted should be decided on an individual basis.
- In the U.S., doctors can reduce the chance of having triplets by using improved techniques, varying the number of embryos by the age of the woman, and allowing the embryo to grow a few extra days before implantation.