Two embryos aren't twice as nice for IVF patients

When couples with fertility problems turn to IVF, they often assume that they can double their chances for a healthy baby by transferring two embryos to the womb instead of just one.

But new data published in Thursday’s edition of the New England Journal of Medicine shows that what they’re really doing is increasing their odds of having twins – an outcome that is riskier for the mother and babies alike.

In the early days of in vitro fertilization, doctors routinely transferred half a dozen – or more – embryos into a patient’s uterus to boost the odds that at least one would implant and grow into a healthy baby. As the treatment improved, doctors were able to get better results using fewer embryos.

Debate lingers about the pros and cons of transferring two embryos instead of just one. As my colleague Shari Roan reported in the Health section in 2007, pregnancies involving multiples come with a greater risk of gestational diabetes, bleeding and preeclampsia for the mother and cerebral palsy, birth defects, developmental delays and death for the babies. Twins usually survive, but incur much higher medical expenses over the first five years of life.

A team of Swedish researchers is trying to assess the optimum number of embryos to transfer during a cycle of in vitro fertilization. In their study of 661 IVF patients, 331 women got two embryos on their first try, and 142 of them (or 43%) had a live birth. The other 330 women got a single embryo, and if that didn’t work, they made a second attempt with another embryo that had been frozen and thawed. Of these women, 128 (or 39%) had a live birth.

The difference between 43% and 39% wasn’t statistically significant. But one-third of the patients in the double-embryo group had twins or triplets, compared with only 1% of patients in the single-embryo group. Those results were published in the New England Journal of Medicine in 2004.

The research team, from Gothenburg, Sweden, continued to follow those 661 patients through as many as four additional IVF cycles (with no restrictions on how many thawed embryos were transferred at a time). In the latest issue of the journal, they offered the final tally.

Their key statistic is the cumulative live birth rate, which measures the number of patients who wound up with at least one live birth divided by the total number of patients. In the group that started out with a double-embryo transfer, the cumulative live birth rate was 51%. In the group that started out with a single transfer, the rate was 44%. As before, the difference wasn’t statistically significant.

Also as before, the difference in multiples was huge. There were four sets of twins in the single-embryo group (for an overall rate of 2.3%) versus 51 sets of twins and one set of triplets in the double-embryo group (for an overall rate of 27.5%).

The researchers conclude that for IVF patients, there’s little downside and plenty of upside to transferring one embryo at a time instead of two.

-- Karen Kaplan

Photo: Doctors performing in vitro fertilization should transfer only one embryo at a time, according to a new analysis. Photo credit: Liz O. Baylen/Los Angeles Times

Comments

[Dawn]

Unless you don't have the money for multiple tries, the more embryos might be ideal. The double embryos had a higher initial pregnancy rate.

[JFS]

This study is clearly applicable in Sweden, as well as other countries that have solid health care access. In the US, the decision to implant two or more embryos is often made by families who are unable to afford multiple rounds of IVF. The resulting overall costs, are, of course, higher. However, those costs are more likely to be covered by insurance...and besides, by the time they happen, the family no longer has a choice. Not to be too polemical, but it is hard not to notice that the patchwork US "non-system" of health care coverage (again) ends up driving up both risks and costs.

[Marna Gatlin]

"A team of Swedish researchers is trying to assess the optimum number of embryos to transfer during a cycle of in vitro fertilization. In their study of 661 IVF patients, 331 women got two embryos on their first try, and 142 of them (or 43%) had a live birth. The other 330 women got a single embryo, and if that didn’t work, they made a second attempt with another embryo that had been frozen and thawed. Of these women, 128 (or 39%) had a live birth."

While I understand the reasons and basis behind the study the part that bothers me is the statistics. In the USA at your clinics that have incredibly high success rates (80% and higher for DE IVF) : San Diego Fertility, Oregon Reproductive Medicine, Colorado Center for Reproductive Medicine money is a factor and money will always be a factor.

When you are spending anywhere from 30-45k for a single IVF cycle for donor egg IVF you want to stack your odds so you have the highest chance of success. Right now that's putting two blastocysts back.

With that being said egg vitrification has made the freezing and thawing process of embryos much better -- and so the success rate of single embryo transfers (SETS) has gone up -- but until insurance companies recognize infertility as a disease and cover IVF cycles -- it's going to be a really hard sell to *most* women to undergo a SET especially when putting back two blasts results in a 80+% success rate.