Cumulative live birth rates following miscarriage in an initial complete cycle of IVF: a retrospective cohort study of 112 549 women.

STUDY QUESTION: In women undergoing IVF/ICSI who miscarry in their first complete cycle, what is the chance of a live birth in subsequent complete cycles, and how does this compare with those whose first complete cycle ends with live birth or without a pregnancy?

SUMMARY ANSWER: After two further complete cycles of IVF/ICSI, women who had miscarried or had a live birth in their first complete cycle had a higher chance of live birth (40.9 and 49.0%, respectively) than those who had no pregnancies (30.1%).

WHAT IS KNOWN ALREADY: Cumulative live birth rates (CLBRs) after one or more complete cycles of IVF have been reported previously, as have some of the risk factors associated with miscarriage, both in general populations and in those undergoing IVF. Chances of cumulative live birth after a number of complete IVF cycles involving replacement of fresh followed by frozen embryos after an initial miscarriage in a population undergoing IVF treatment have not been reported previously.

STUDY DESIGN, SIZE, DURATION: National population-based cohort study of 112 549 women who started their first IVF treatment between 1999 and 2008.

PARTICIPANTS/MATERIALS, SETTING, METHODS: Data from the UK Human Fertilisation and Embryology Authority (HFEA) register on IVF/ICSI treatments, using autologous gametes were analysed. CLBRs were estimated in women who (i) had miscarriage (and no live birth), (ii) at least one live birth or (iii) no pregnancy in their first complete cycle of IVF/ICSI (including fresh and frozen embryo transfers following a single oocyte retrieval episode). A multivariable analysis was performed to assess the effect of first complete cycle outcome on subsequent CLBRs after adjusting for confounding factors such as female age, duration of infertility and cause of infertility.

MAIN RESULTS AND THE ROLE OF CHANCE: In their first complete cycle, 9321 (8.3%) women had at least one miscarriage (and no live birth); 33 152 (29.5%) had at least one live birth and 70 076 (62.3%) had no pregnancies. After two further complete cycles, conservative CLBRs (which assume that women who discontinued treatment subsequently never had a live birth) were 40.9, 49.0 and 30.1%, while optimal CLBRs (which assume that women who discontinue have the same chance of live birth as those treated) were 49.5, 57.9 and 38.4% in the miscarriage, live birth and no pregnancy groups respectively. Odds of cumulative live birth for women who miscarried in their first complete cycle were 42% higher than those who had no pregnancy [odds ratio (95% CI) = 1.42 (1.34, 1.50)], and twice as high for live birth versus no pregnancy [2.04 (1.89, 2.20)]. Negative predictors for live birth in all women included tubal infertility [0.88 (0.82, 0.94)] and increasing age [18-40 years = 0.94 (0.94, 0.95); >40 years = 0.63 (0.59, 0.66) per year].

LIMITATIONS AND REASON FOR CAUTION: CLBRs could not be estimated for treatments occurring after September 2008 due to potentially incomplete data following regulatory changes regarding consent for data use in research. Additionally, covariates not included in the HFEA database (including BMI, smoking, previous history of miscarriage and gestational age at miscarriage) could not be adjusted for in our analysis.

WIDER IMPLICATIONS OF THE FINDINGS: Miscarriage following IVF can be devastating for couples who are uncertain about their ultimate prognosis. Our findings will provide reassurance to these couples as they consider their options for continuing treatment.

STUDY FUNDING/COMPETING INTEREST(S): N.J.C. received an Aberdeen Summer Research Scholarship funded by the Institute of Applied Health Sciences (University of Aberdeen), through the Aberdeen Clinical Academic Training Scheme. This work was supported 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 or the University of Aberdeen. The funders did not have any role in the study design; in the collection, analysis and interpretation of data; in the writing of the report; nor in the decision to submit the paper for publication. None of the authors has any conflicts of interest to declare.