A prediction model for selecting patients undergoing in vitro fertilization for elective single embryo transfer

Objective: Construction of a prediction model to enable the selection of patients for elective single ET. Design: Retrospective cohort study. Setting: Fertility center in a tertiary referral University hospital. Patient(s): Six hundred forty-two women undergoing their first IVF treatment cycle in which no more than two embryos were transferred. Intervention(s): Database analysis. Main Outcome Measure(s): Ongoing pregnancy and multiple pregnancy. Result(s): In multivariate analysis, the best predictors for ongoing pregnancy were female age, the number of retrieved oocytes, the developmental stage score and the morphology score of the two best embryos available for transfer, and the day of transfer. Younger age and high quality of transferred embryos were the best predictors for increased risk of multiple pregnancy. The resulting model enables the calculation of probabilities of pregnancy and twin pregnancy. Depending on embryo quality, there is a threshold age under which the chance of singleton pregnancy is higher if one embryo is transferred compared with two embryos. Conclusion(s): Application of this model may enable a reduction in the chance of twin pregnancy without compromising singleton pregnancy rates in a subgroup of patients undergoing IVF.