Results
Out of 995 women who met the selection criteria, 509 women used the PPOS protocol while 486 women used the long agonist protocol. One woman in the PPOS group had premature ovulation before oocyte retrieval. No transferable embryos were available in 61women in the PPOS group and 19 women in the long agonist group resulting in cycle cancellation, the cancellation rate was significantly higher in the PPOS group than in the agonist group (12.0% versus 3.9%, p < 0.001). Within 18 mouth follow up, 76 (14.9%)women in the PPOS group and 55 (11.3%) women in the agonist group who did not achieve live birth but still have cryopreserved embryos were also included for analysis (Figure1).
Demographic and the index stimulation cycle characteristics
Baseline characteristics of two groups are presented in Table I. No significant differences were found with regard to age of women, basal AFC, basal FSH level, number of previous IVF cycles, body mass index, cause of infertility, proportion of primary infertility and insemination methods between the two groups except for duration of infertility, which was significantly shorter in the PPOS group compared to that in the long agonist group.
The starting dose of FSH was higher (225 IU versus 150 IU, P < 0.001), days of stimulation is shorter (8 days versus 11 days, P < 0.001) and total FSH dose was lower (1800 IU versus 2025 IU, P < 0.001) in the PPOS group compared to those in agonist group. Serum estradiol levels (2740 pg / ml versus 2496 pg / ml, P < 0.05) and LH level on HCG day (2.6 IU/ml versus 0.7 IU/ml, P < 0.001) was higher in the PPOS groups than those in the long agonist group. However, there was no significant difference in the serum progesterone level on the hCG day between the two groups. One women in the PPOS groups experienced premature LH surge while none was seen in the long agonist group. No patient experienced OHSS in the PPOS groups, while 4 patients (0.8%) in the long agonist group were administered into hospital due to moderate or severe OHSS. (Table 1)
Average number of oocytes obtained (9 versus 12, P < 0.001), number of oocytes fertilized (7 versus 8, P < 0.001), number of cleaving embryos (6 versus 8, P < 0.001) and number of transferable embryos (3 versus 4, P < 0.001) was lower in the PPOS group as compared to that in the long agonist group. However, no differences were found in fertilization rate, cleavage rate, number of blastocyst formation and number of good quality embryos between the two groups (Table I) .