OULU, Finland - Single-embryo transfer during in-vitro fertilization is just as likely to result in pregnancy and a live birth among women ages 36 to 39 as it is for younger women, researchers reported.
OULU, Finland, June 1 - Single-embryo transfer during in-vitro fertilization is just as likely to result in pregnancy and a live birth in women ages 36 to 39 as it is for younger women, researchers reported.
Randomized trials have shown that the single-embryo technique is effective in women younger than 35, but little had been known about whether the technique's success rate applied to older women as well, said Hannu Martikainen and colleagues at the University of Oulu and at Helsinki University.
In a series of analyses of 1,224 fresh IVF single-embryo cycles and 828 frozen single-embryo transfers among women 36 to 39, the single-embryo transfers were found equal to 585 double-embryo transfers, the researchers reported in the June 1 issue of Human Reproduction.
Significantly, the researchers said, the likelihood of pregnancy and a live birth after transferring a single embryo to a woman's womb was also similar to results reported for younger women.
In the study, which analyzed a variety of cycles, the major fresh cycle, consisting of 335 single top-quality embryo transfers, was compared with the 585 double-embryo transfers.
The pregnancy rates did not differ significantly between the single- and double-embryo groups. The pregnancy rate was 33.1% (111/335) for the single-embryo transfers versus 29.9% (175/585, P=0.3) for the double-embryo group.
The live birth rates for the single- and double-embryo groups were also similar: 26.0% (87/335) versus 22.4% (131/585, P=0.2), the investigators reported.
However, women in the single-embryo group had a higher cumulative pregnancy rate (54% vs. 35%) and a higher cumulative birth rate (41.8% versus 26.7%, P<0.0001) compared with those in the double-embryo group. The cumulative rate included results for women who had more than one cycle of treatment and who used fresh or frozen embryos.
The cumulative multiple birth rate among the single-embryo women was 1.7%, whereas in the dual-embryo group, it was 16.6% (P<0.0001).
"This rate of almost 2% versus nearly 17% tells us that not only is the risk of multiple births reduced in single-embryo transfer but the safety of assisted reproduction is increased in this age group," Dr. Martikainen said.
One of the most serious complications of IVF treatment is the high multiple birth rate, which leads to increased perinatal mortality and morbidity, as well as maternal complications. Multiple pregnancies represent an increased health risk for older women, because the frequency of complications such as gestational diabetes and pre-eclampsia is higher. In singleton pregnancies, the risk of pre-eclampsia increases by 30% for every additional year past 34 years and is three times higher in the presence of a twin pregnancy, the researchers wrote.
The present study found that in this older age group of 36 to 39, a clinical pregnancy rate of 33% after single-embryo transfer was similar to that of 30.8% to 34.5% reported in studies of younger women. When frozen embryo transfer was included, the cumulative pregnancy rate among the older women was 54% with a live birth rate of over 40%, a rate that is satisfactory, Dr. Martikainen and colleagues said.
These findings suggested that embryo quality is the most important parameter in the outcome and that selection for elective single- embryo transfer should be based on morphology rather than the woman's age-at least until age 40, the researchers said.
It is still rational, the researchers added, to use double embryo transfer in certain circumstances. The researchers said they use the single-embryo method in about 40% of women ages 36 to 39 and in about 60% of younger women, with a multiple pregnancy rate of less than 10%.