A validated prediction score for having two or more embryos for cryopreservation following freeze-all IVF cycles: an analysis utilizing SART CORS database

Purpose: To develop and validate a prediction score for having 2 or more embryos cryopreserved following an IVF cycle without a fresh transfer such that an embryo selection method may be applicable. We also developed a counseling tool on the probability of not having any embryos following an IVF cycle without a fresh transfer. Methods: We split the data into a development set and a validation set by region within the USA using a coin flip approach and subsequently performed a logistic regression model to identify factors most predictive of cryopreservation of 2 or more embryos in the development set. This model was validated in the validation set. Subsequently, a clinical prediction score was derived using the model coefficients and the predictive accuracy measured with the concordance (c) statistic. Results: A total of 31,537 potential freeze-all cycles were reported to the Society for Assisted Reproductive Technology in 2014. Of these, 57.87% produced and cryopreserved two or more embryos. We identified that age, AMH, and the number of eggs retrieved were the most significant predictors of having 2 or more embryos cryopreserved with a validated c-statistic of 0.84 (95% CI: 0.83 to 0.85). A clinical prediction score was derived from the model. 28.9% of freeze-all cycles had no embryos created from the IVF cycle despite a cycle start and an egg retrieval. The number of eggs retrieved was the most significant predictor of having no embryos available for a transfer, with a c-statistic of 0.80 when modeled as the only predictor variable. Conclusion: We derived counseling tools with acceptable discrimination for use in clinical practice (c-statistics > 0.7). Our study further suggests that the number of eggs retrieved from an IVF cycle is most predictive of having 2 or more embryos cryopreserved and not having any embryos after an IVF cycle, suggesting that clinicians should strive to optimize oocyte yield especially in poor prognosis patients. The probability of having two more embryos cryopreserved in a freeze-all IVF cycle such that an embryo selection method is applicable can be predicted with acceptable precision prior to the IVF cycle and excellent precision following egg retrieval using the prediction score.