Cumulative live birth rates after one or more complete cycles of IVF: a population-based study of linked cycle data from 178,898 women.

STUDY QUESTION: What is the chance of a live birth following one or more linked complete cycles of IVF (including ICSI)? SUMMARY ANSWER: The chance of a live birth after three complete cycles of IVF was 42.3% for treatment commencing from 1999 to 2007. WHAT IS KNOWN ALREADY: IVF success has generally been reported on the basis of live birth rates after a single episode of treatment resulting in the transfer of a fresh embryo. This fails to capture the real chance of having a baby after a number of complete cycles-each involving the replacement of fresh as well as frozen-thawed embryos. STUDY DESIGN, SIZE AND DURATION: Population-based observational cohort study of 178 898 women between 1992 and 2007. PARTICIPANTS/MATERIALS, SETTING,
METHODS: Participants included all women who commenced IVF treatment at a licenced clinic in the UK as recorded in the Human Fertilisation and Embryology Authority (HFEA) national database. Exclusion criteria included women whose treatment involved donor insemination, egg donation, surrogacy and the transfer of more than three embryos. Cumulative rates of live birth, term (>37 weeks) singleton live birth, and multiple pregnancy were estimated for two time-periods, 1992-1998 and 1999-2007. Conservative estimates assumed that women who did not return for IVF would not have the outcome of interest while optimal estimates assumed that these women would have similar outcome rates to those who continued IVF. MAIN RESULTS AND THE ROLE OF CHANCE: A total of 71 551 women commenced IVF treatment during 1992-1998 and an additional 107 347 during 1999-2007. After the third complete IVF cycle (defined as three fresh IVF treatments-including replacement of any surplus frozen-thawed embryos), the conservative CLBR in women who commenced IVF during 1992-1998 was 30.8% increasing to 42.3% during 1999-2007. The optimal CLBRs were 44.6 and 57.1%, respectively. After eight complete cycles the optimal CLBR was 82.4% in the latter time period. The conservative rate for multiple pregnancy per pregnant woman fell from 31.9% during the earlier time period to 26.2% during the latter. LIMITATIONS AND REASON FOR CAUTION: Linkage of all IVF treatments to individual women was conducted. However, it was not possible to identify with certainty in all cases the episode of ovarian stimulation which generated some of the frozen embryos. Cumulative live birth rates could not be calculated for women who started treatment beyond 2007 as follow-up data were incomplete in some of them. Following a change in legislation in 2008, linked data were only made available for research in women who gave formal consent for this purpose. BMI and ethnicity could not be reported: these demographics are not recorded in the HFEA database. WIDER IMPLICATIONS OF THE
FINDINGS: Our results demonstrate, at a national level, the chances of live birth in couples undergoing a number of complete (fresh and frozen) IVF cycles. They reflect improvements in reproductive technology and a more conservative embryo transfer policy. Although most couples in the UK still do not receive three complete IVF cycles; assuming no barriers to continuation of IVF treatment, around 83% of women receiving IVF would achieve a live birth by the eighth complete cycle, similar to the natural live birth rate in a non-contraception practising population. Our results support the call from NICE to develop consistent IVF policies based on three complete cycles. STUDY FUNDING/COMPETING INTERESTS: This work was funded by a Chief Scientist Office Postdoctoral Training Fellowship in Health Services Research and Health of the Public Research (Ref PDF/12/06). The views expressed here are those of the authors and not necessarily those of the Chief Scientist Office. S.B. reports grants from Chief Scientist Office Scotland during the conduct of the study. His institution has received support from Pharmaceutical companies (for educational seminars), which is not related to the submitted work. D.J.M., A.M. and A.J.L. have no conflicts of interest to declare.