Results
Both groups had almost comparable demographic and cycle stimulation characteristics. The ongoing pregnancy (34.0 % (49/114) vs 42.3% (52/123), P=0.166, RR=0.81(0.59-1.09)), clinical pregnancy (38.2% (55/144) vs 44.7% (55/123), P=0.281, RR=0.85 (0.64-1.14)) and implantation (29.5% (75/254) vs 31.6% (68/215), P=0.623, RR=0.93 (0.71-1.22)) rates were comparable between the PPOS group and the antagonist group respectively. In order to control the difference in demographic and index stimulated IVF cycle characteristics, a multivariate logistic regression revealed that only the stimulation protocol and number of embryos replaced were significant factors in predicting the ongoing pregnancy.