For the first time, researchers in the USA have calculated cumulative success rates of infertility treatments that use IVF or assisted reproductive technologies (ART), and have showed that overall success rates come close to that of natural conception.
The study was led by Barbara Luke, professor of obstetrics, gynaecology and reproductive biology at Michigan State University, and was published in the New England Journal of Medicine.
The results show that the cumulative live birth rate using ART, under optimal conditions, was 75 percent after three cycles of treatment. However, this rate increased to 81 percent when transferring blastocyst embryos (transferred on day five or six) compared to 65 percent for cleavage embryos (transferred on day two or three). The estimated rates of conceiving naturally are 45 percent, 65 percent and 85 percent after three, six and 12 months, respectively.
Until now, success rates have been reported on a per cycle basis - currently about 30 percent - which does not give patients information on their chance of a live birth after multiple cycles. However, as Professor Luke points out, 'women and families want to know the overall chances they will get pregnant, not necessarily whether they will get pregnant during a specific cycle'.
Around 25 percent of patients cease treatment after the first cycle owing to reasons including stress and cost, with insurers in the USA only covering two or three cycles of treatment. The knowledge of overall success rates could help patients in their decision to continue with treatment and guide health insurance regulations.
The study highlighted the decrease in live-birth rates as maternal age increases. By the third cycle, women of 31 or younger had 75 percent live birth rates compared to 28 percent for those aged 41 to 42 and 11 percent for those aged over 43.
Dr Luke said: 'As we age, our eggs age, and the quality of the embryo may be less. That's why using a donor egg, from a younger women, greatly improves the live birth rate among older women'. Indeed, the authors found that live birth rate was independent of age when using donor eggs.
Live birth rates were also found to be highest when two embryos were implanted (77 percent) compared to one or three. Although the authors note that this would increase the chance of multiple births and associated risks this could incur.
The lowest rates of live births were among those women whose infertility was caused by uterine factors or diminished reserve of oocytes, showing that uterine environment was still an important factor.
The study was based on data from the Society for Assisted Reproductive Technology (SART) Clinic Outcome Reporting System database for 246,740 American women who were treated with ART between 2004 and 2009. The large size of this study allowed the researchers to compare the effects of the number of embryos transferred, the day of transfer and the use of previously frozen eggs.
Dr Glen Schattman, president of SART and a co-author of the study, said the results provide patients with 'important and encouraging information'. He added: 'While tracking outcomes by cycle started or single embryo transfer is a valuable method for assessing quality, having cumulative data linked to individual patients better estimates the prospect for success when they start a treatment cycle'.