In this procedure, complete cycle number, the woman’s age, duration of infertility, and number of eggs collected (for post-treatment model only) were always included and could not be removed because these are known predictors of pregnancy outcomes after IVF.12 All of the other available predictors (listed as baseline characteristic) were subjected to the selection process.
Women who had no eggs collected were excluded from the post-treatment model because it would not be possible to achieve a live birth in the first complete cycle.
Pretreatment, a 30 year old woman with two years of unexplained primary infertility has a 46% chance of having a live birth from the first complete cycle of IVF and a 79% chance over three complete cycles.
If she then has five eggs collected in her first complete cycle followed by a single cleavage stage embryo transfer (with no embryos left for freezing) her chances change to 28% and 56%, respectively.
Main outcome measure Two clinical prediction models were developed to estimate the individualised cumulative chance of a first live birth over a maximum of six complete cycles of IVF—one model using information available before starting treatment and the other based on additional information collected during the first IVF attempt.
Supplementary figure A1 details further exclusion criteria made on receipt of the data.
Therefore we fitted a separate model for these women.