For many couples with infertility problems, twins sound like a great deal. Doctors who treat them often say their patients describe a multiples pregnancy as an "instant family" or "two for the price of one."

But what looks like a bargain to patients is seen as a complication by fertility doctors, who know that multiples pregnancies are risky for mothers and their babies. Multiples come with increased chances of birth defects, lung damage and neurological disorders, among other health troubles.

"Most people come in wanting multiples," said Dr. Joseph Hill, the medical director of Fertility Centers of New England, a practice with offices in Bedford and Portsmouth. "It's expensive, they want to get it done with. They want to do it once and be done with it."

New research shows that if patients are willing to choose a particular fertility procedure called single-embryo transfer, they can virtually eliminate their chance of bearing twins or triplets. But persuading patients to sign up has been a challenge, many local infertility doctors said.

On the surface, it's easy to see why patients might favor multiples. Infertility treatment, especially the in vitro fertilization procedures that Hill's practice offers, are expensive and time-consuming. In New Hampshire, where insurers are not required to pay for infertility treatment, almost all patients must pay out-of-pocket for IVF treatments at a cost of $7,000 to $12,000 a month. Patients want to increase their odds that each round of treatment will end in pregnancy. If they're hoping for two children eventually, why not have them at once, for one price tag?

And many patients have options that are even less expensive than a single cycle of IVF. Women with certain infertility conditions can choose medications that boost their egg production. The upside of the treatment is it can be done in a local gynecologist's office, at a much lower cost than IVF - about $5,000 for three cycles. The downside is that ovary-stimulating drugs carry an even higher risk of multiples than IVF. They were responsible for about two-thirds of all triplets and higher-order multiples born in 2003, according to data from the Centers for Disease Control and Prevention.

During in vitro fertilization, doctors remove eggs from a woman and sperm from a man, combine them in a laboratory, and insert one or more of the resulting embryos into the woman's uterus. It was once common practice to give every woman at least three embryos, in hopes of boosting the chances that any one would "take." As technologies have improved, more and more of those embryos were turning into fetuses, resulting in sharp increase in multiples pregnancies. Recent studies have placed the odds of a twin pregnancy between 25 and 40 percent when doctors inserted two embryos.

Now, a small group of doctors will routinely transfer just one embryo in younger patients, a process that virtually guarantees that if the mother gets pregnant, she'll have only one baby.

"It was becoming more and more obvious to us that to be very successful in our field, we wanted to mimic nature - and to mimic nature was to have single pregnancies at once," said Dr. Thomas Toth, the director of the Vincent IVF program at Massachusetts General Hospital, where 25 percent of their patients get the single-embryo transfer procedure. "Patients can be very concerned about pregnancy rates and will do just about anything. I think the focus of our energies should be on having the safest pregnancies rather than the highest pregnancy rates."

Single-embryo transfers have been slow to catch on. They represented just 2 percent of all IVF cycles nationwide, according to CDC statistics for 2005. In several European countries, where the governments regulate the number of embryos that can be transferred, research has shown high pregnancy rates for the single-embryo procedure, especially over a few cycles.

Now researchers at Massachusetts General and at the University of Iowa, another academic hospital with 25 percent single-embryo transfer rates, are both poised to publish papers demonstrating the success of the technique in their practices in the United States.

Brad Van Voorhis, director of reproductive endocrinology at the University of Iowa, said his research found that in the right patient population, single-embryo transfers resulted in a pregnancy rate of more than 65 percent. His group's article will be published in the journal Fertility and Sterility next month.

"I hope people read the article and come away impressed that it can be successful," Van Voorhis said. "I hope that single-embryo transfers are done more commonly throughout the country."

Similar research about the success of double-embryo transfers a few years ago was persuasive enough that the Society for Assisted Reproductive Technology, the professional association for IVF doctors, changed its practice recommendations in 1998. Now, the society recommends that doctors place only two embryos in women under 35 with good prognoses. That change in policy may be responsible for a slight decline in triplets births since 1999.

Cost concerns

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