BACKGROUND: Knowing predictors of pregnancy in IVF is helpful for clinicians to individualize the treatment plans and improve patient counseling and for patients to decide whether to undergo infertility treatment. The aim of the study was to identify independent predictors of the chance of clinical pregnancy after a completed IVF/ICSI cycle (fresh plus cryopreserved embryos transferred from one stimulated cycle) and to compare the predictive value of important predictors identified. METHODS: This was a single center, retrospective study of 2450 infertile women undergoing their first IVF treatment between 2002 and 2007. A bootstrapping stepwise variable selection algorithm was performed to identify independent predictors of clinical pregnancy chance from a list of 27 candidate variables. Multivariable logistic regression was used for assessing the effects of predictors. Proportion of explained variation analysis and concordance index were adopted to compare the predictive value of factors. RESULTS: The following nine independent predictors were included in the final multivariable model: total number of good-quality embryos, total number of embryos, age, antral follicle count, fertilization rate, duration of infertility, endometrial thickness, number of 10-14-mm follicles and progesterone level on the day of hCG injection. The model was cross-validated internally in the training data and validated externally in an independent data with robust performance. The stratified analysis demonstrated that the total number of good-quality embryos was a better predictor of clinical pregnancy chance after a completed IVF/ICSI cycle than age for women,40 years, whereas age was a better predictor for women >= 40 years. The restricted cubic spline analysis revealed the relationship between the total number of good-quality embryos and log-odds of achieving a clinical pregnancy was nonlinear. CONCLUSIONS: Quality and quantity of the whole embryos are the two most important predictors of the cumulative outcome in IVF/ICSI among independent predictors indentified. The importance of embryo quality on cumulative outcome in IVF/ICSI increases with increasing age.