Life table (survival) analysis to generate cumulative pregnancy rates in assisted reproduction: are we overestimating our success rates?

The variability in the numbers of treatment cycles couples may undertake with assisted reproductive technology (ART) and the length of time they may have to wait between successive cycles of treatment make the evaluation of treatment efficacy and prognosis complicated. The cumulative pregnancy rate using the life table method of analysis is being used more frequently to estimate the effectiveness of treatment. Although this approach is valid in some areas of infertility research, its use in ART is not appropriate, because the factors necessary for the analysis (particularly the scale for measuring the passage of time and lack of informative censoring) are not satisfied. Consequently, an overestimation of the effect of treatment is produced that may lead to biased decision making. Although there is no easy solution to this problem, several options for summarizing the outcome data are offered: pregnancy rate per cycle, time-limited analysis using proportions, conservative cycle-based cumulative pregnancy rate and real-time-based cumulative pregnancy rate. In this manner, more realistic information can be generated to counsel patients, evaluate the efficacy of treatments, compare rates among centres and guide the formulation of policies for infertility management and resource allocation.