Large blastocyst diameter, early blastulation, and low preovulatory serum progesterone are dominant predictors of clinical pregnancy in fresh autologous cycles

Objective: To identify dominant predictors of clinical pregnancy in IVF cycles. Design: Retrospective study. Setting: Private fertility center. Patient(s): The study included 580 fresh autologous IVF cycles with blastocyst transfer. Intervention(s): None. Main Outcome Measure(s): Clinical pregnancy rate. Result(s): A set of 25 suspected predictors was used to develop predictive models of clinical pregnancy in a set of 361 blastocyst transfer cycles. Initial bivariate analysis identified 14 of these variables that were significant enough to be candidate variables for multiple logistic regression. Similar sets of significant variables were identified by using alternative approaches for model construction. The final model included blastocyst diameter, day of blastulation, and preovulatory serum P level as significant predictors of clinical pregnancy. Specifically, clinical pregnancy was predicted by preovulatory serum P of < 1.0 ng/mL, blastulation on day 5, and large blastocyst diameter. Of these variables, blastocyst diameter was the most significant predictor of clinical pregnancy in the multivariate models. The final model was validated against a separate set of 219 subsequent blastocyst transfer cycles. Conclusion(s): Pre-ovulatory serum P level, blastulation day, and embryo diameter are simultaneously predictive of clinical pregnancy, and their relationships with clinical pregnancy are consistent with an effect of embryoendometrium synchrony.