Shortly after Nadya Suleman gave birth to octuplets in January 2009, the children's births went from being miraculous to being scandalous. Word spread that her doctor implanted the so-called "Octomom" with six embryos through in vitro fertilization (IVF).
One of the main reasons the Octomom case generated so much controversy is that fertility experts say the trend in the field of reproductive medicinehas been steadily moving away from multiple embryo transfers.
"The single embryo transfer is the way of the future," said Dr. Jeffrey Fisch, medical director of the Sher Institute for Reproductive Medicine in Las Vegas, Nev.
A new study published in the British Medical Journal validates that growing trend. The study found that only 27 percent of women who received single embryos gave birth to babies, compared to 42 percent of women who received two embryos -- but multiple embryo implants also accounted for about far more multiple births, which are associated with medical complications including a higher risk of pre-term delivery and gestational diabetes.
If a single embryo transfer is unsuccessful and is followed by a frozen embryo transfer, however, the birth rate is about equal to the birth rate of double embryo transfers, however.
Doctors say the study offers proof that single embryo transfers are an effective and safer way for women to have children through in vitro fertilization, though it's difficult to convince patients.
"It's a useful study," said Fisch. "Anything that moves the public in general to accept the idea that one embryo can make a baby is a move forward."
The researchers, led by David McLernon, a research fellow in medical statistics at the University of Aberdeen in Scotland, analyzed eight different studies that compared the outcomes of single embryo transfers to double embryo transfers. More than 1,300 women were included in the analysis.
All the women in the study received embryos that were two or three days old. Fertility experts say that used to be the most common type of transfer, but now, more and more women are getting embryos that are five days old.
"There's natural selection that occurs, so the embryos that survive to day five are the most viable and likely to survive through pregnancy," said Dr. Jamie Grifo, director of the fertility center at New York University Langone Medical Center.
Grifo said that more recent studies, including one he co-authored, show that five-day-old embryos are associated with a 63 percent pregnancy rate, a rate he says is higher than for two- or three-day-old embryos.
"The [current study's] biggest limitation is that they're looking at earlier stage embryos and there's a move in the field to move toward five-day embryo transfer," said Fisch.
In an accompanying editorial, Allan Templeton, professor of obstetrics and gynecology at the University of Aberdeen, said many fertility specialists are more concerned with birth rates than patient safety. As a result, he said, they don't stress the importance of single embryo transfers. He said single embryo transfer rates are the lowest in the U.S.