Spanish Study: Stronger Embryo May Help The Weaker One To Survive Via IVF

10.01.2012

A controversial new study suggests that when twin pregnancies are created by in vitro fertilization (IVF), a stronger embryo may help the weaker one to survive.

Researchers from Spain found that the overall rate of survival rate for embryos was 83 percent in twin pregnancies vs. 76 percent for a solo child. The number of successful double births in twin pregnancies was higher than researcher should have expected, based on statistical analysis, while the number of single births was lower than expected.

The results, as written in the journal Obstetrics and Gynecology, appear to indicate that feeble embryos that might fail on their own receive support from their stronger twin in some way.

Even though several studies have found that twin pregnancies result in higher live birth rates, at least one expert not involved in the study expressed doubt in the theoretical idea of “embryo assistance”.

About one percent of U.S. births are babies conceived through IVF, according to researchers, but IVF accounts for about 17 percent of twins.

More than one embryo is often impanted by doctors to increase the chances of a successful pregnancy, but clinics have recently been reducing the number of embryos they put into women due to the risks that multiple pregnancies carry for fetuses.

The American Society for Reproductive Medicine recommends that for women under 35, no more than two embryos should be implanted and doctors should consider using just one.

A study from an Iowa fertility center earlier this year found no drop in successful pregnancies after it started using the single-embryo policy.

For the new study, data from 1,159 single and 523 twin pregnancies (fraternal twins, not identical twins) was studied. Of the twin pregnancies 72 percent yielded double live births, while only a rate of 58 percent was expected.

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