LONDON (AP) — A new study of fertility treatment found that women who get three or more embryos have no better odds of having a baby than those who get just two embryos.
They also have a greater chance of risky multiple births.
"Women who have gone through infertility treatment want the best chance of having a baby, but we need to explain that the data shows transferring more embryos doesn't actually do that," said Dr. Scott Nelson, head of reproductive and maternal medicine at the University of Glasgow, who co-authored the study published in Thursday's issue of Lancet.
In Western Europe, where some countries pay for in-vitro fertilization, or IVF, many authorities recommend a single embryo transfer for women under 37 and a maximum of two embryos for women 37 to 40. For women over 40, three is often the limit by law.
In the United States, there are relatively lax guidelines and a lack of regulation. That country has seen a rise in multiple births, including the highly publicized case of Nadya Suleman, labeled the "octomom." She had octuplets in 2009 after her doctor transferred 12 embryos. She already had six children through IVF.
Most fertility treatment in the U.S. is paid for privately and can cost at least $10,000 per cycle, which experts believe encourages the use of more embryos in the belief it will improve odds.
The American Society for Reproductive Medicine recommends single embryo transfers for women under 35, but there is no enforcement of that. For women 35 to 37, they advise two to three embryos, and three to four embryos for women ages 38 to 40.
In their study, Nelson and Debbie Lawlor, of the University of Bristol, analyzed data for all 124,000 IVF cycles in the U.K. between 2003 and 2007, resulting in more than 33,500 live births. The women were 18 to 50 and had varying histories of infertility. During IVF, eggs are fertilized with sperm in a lab dish and then put in the womb.
For women under 40 who had two embryos transferred, the live birth rate was 33 percent overall. With three embryos, that dropped to 25 percent, though researchers weren't sure why. Nelson said it might be due to the higher risk of miscarriage in a multiple pregnancy and that miscarrying one fetus would jeopardize the entire pregnancy.
For women over 40, the live birth rate was 13 percent whether they had two or three embryos transferred.
Nelson said patients going through IVF may pressure doctors to transfer more embryos, believing it may boost their chances of having a baby and avoiding more treatment.
"Doctors may feel if they don't do what their patients want, they'll just go down the street to another clinic," he said. "They need legislation to help control the situation."
The U.K. has tougher policies. Transferring three embryos in women under 40 is banned. And if doctors transfer more than three embryos, they must explain their actions to the fertility regulator. In 2010, about 65 percent of embryo transfers involved two embryos and 4 percent used three. The rest were single embryos.
In the U.S., data from 2009 showed about 52 percent of embryo transfers involved two while 23 percent used three embryos. Nearly 12 percent involved four to seven or more embryos. Only about 14 percent used one.
Multiple births have a higher risk of problems, including an increased chance of miscarriage and pregnancy complications like high blood pressure and diabetes. Twins and triplets are more likely to be premature and have an increased risk of developmental problems such as cerebral palsy.
Dr. James Grifo, director of the New York University Fertility Center, agreed doctors should avoid using more than three embryos. But he said it was warranted for some, such as older women with a history of failed treatment.
Grifo said the fact many Americans pay for their treatment out of pocket makes a big difference. "I spend a lot of time trying to talk patients out of the three-embryo transfer and you can't always do it," he said.
"My last set of triplets was a patient who demanded I put back three embryos," he said.
Grifo said she wasn't swayed by the data. "She delivered the triplets and they're fine, but I wasn't happy about it."
<한글기사>
英연구 '체외수정 배아, 2개가 적당'
(연합뉴스) 불임치료에 사용되는 체외수정 배아는 2개를 자궁에 주입하는 것이 가장 적당하는 조사결과가 나왔다.
영국 글래스고 대학 의과대학 생식-모성의학과의 스캇 넬슨(Scott Nelson) 박사는 2003-2007년 사이에 영국에서 불임치료 클리닉에서 시행된 12만4천 건의 체외수정 시술사이클 자료를 분석한 결과 40대 이하와 이상 여성 모두 2개 배아 주입이 단일 배아 주입보다 출산성공률이 높은 것으로 나타났다고 밝혔다.
또 3개의 배아를 사용했을 때는 40세 이하 여성은 2개의 배아를 사용한 경우보다 출산성공률이 낮고 40세 이상은 비슷한 것으로 나타났다.
40세 이하는 2개의 배아를 사용했을 때 출산성공률이 33%였고 3개의 배아를 사용했을 때는 출산성공률이 25%로 떨어졌다.
3개의 배아를 주입하면 다태임신 가능성과 함께 유산위험이 높아자기 때문으로 보인다고 넬슨 박사는 설명했다.
40세 이상은 사용한 배아가 2개이든 3개이든 출산성공률이 13%로 같았다.
영국은 체외수정 배아 사용이 엄격하게 제한돼 40세 이하는 3개의 배아를 주입하는 것이 금지되어 있다. 2010년의 경우 2개 배아 사용이 65%로 가장 많았고 3개 배아 사용은 4%, 나머지는 단일 배아가 사용되었다.
미국은 지침이 다소 느슨해 2009년의 경우 2개 배아 사용이 52%, 3개 배아 사용은 23%, 4-7개 또는 그 이상 사용도 12%나 되었다. 단일 배아 사용은 14%였다.
불임치료 클리닉에서는 출산성공률을 높이기 위해 배아를 2개 이상 주입하는 경우가 적지 않다.미국에서는 한꺼번에 12개의 배아를 주입해 2009년 8쌍둥이를 출산한 여성이 있었다.
다태출산은 유산 외에도 자간전증, 임신성당뇨 같은 합병증 위험이 높고 쌍둥이나 세쌍둥이는 조산 가능성과 함께 뇌성마비 같은 발달장애를 가지고 태어날 위험이 크다.
연구결과는 영국의 의학전문지 '랜싯(Lancet)' 최신호(1월12일자)에 발표되었다.
