1. Study design
1. This study retrospectively analyzed 658 treatment cycles of fresh embryo transfer cycle with GnRH antagonist protocol from 2015 to 2020 in the Reproductive Medicine Center of the University of Hong Kong-Shenzhen Hospital. Each cycle was the first fresh stimulation cycle of the patients. The recruitment criteria include: the GnRH antagonist IVF/ICSI protocol with fresh embryo transfer cycles, which should have complete clinical data and complete follow-up information. Exclusion criteria: Other stimulation regimens, GnRH antagonist protocol with all embryo frozen cycles, midway cancelled cycles and cancelled cycles on the trigger day, the cycles with incomplete clinical data or follow-up information.
According to the different luteal phase support regimen, the GnRH antagonist with fresh embryo transfer cycles was divided into the study group and the control group. The study group included 368 cycles with 30 mg oral dydrogesterone daily, while the control group included 290 cycles with 90 mg of progesterone vaginal gel and 20 mg oral dydrogesterone daily.
2. Ethical approval
This study complies with the Declaration of Helsinki. It was approved by the Ethics Committee of the University of Hong Kong-Shenzhen Hospital with the approval number: [2022] 251.
3. Superovulation stimulation protocol
3.1. GnRH Antagonist protocol:
On the day 2 or day 3 of menstrual cycle, the serum concentration of follicle stimulating hormone (FSH), luteinizing hormone (LH), estradiol (E) and progesterone (progesterone, P) were tested, the transvaginal ultrasound was performed to count the antral follicle count (AFC). If AFC ≤6, the recombinant FSH (r-FSH) 300 IU was administrated to initiate superovulation; if 6<AFC<15, 225 r-FSH was administrated; if AFC ≥15, 150 IU r-FSH was administrated. The r-FSH was chosen from Gonalfin (Merck Serono) or Puregon (MSD). As the fixed antagonist protocol, the antagonist ganirelix acetate 0.25 mg/day (Merck & Co.) started from the sixth day of r-FSH administration. When the average diameter of one dominant follicle is ≥ 18 mm, and the average diameter of the other two dominant follicles is ≥ 16 mm, the administration of gonadotropin (Gn) was stopped, and human chorionic gonadotropin is administered. 36 hours later oocyte retrieval was performed. If the estradiol level is lower than 6810 pg/ml (20000 pmol/ml) or the progesterone level is lower than 2.0 ng/ml on the day of trigger. The day 2 cleavage stage embryo or day 5 blastocyst transfer will be performed after oocyte retrieval, if the patient is less than 35 years old, single embryo transfer is performed, if the patient is more than 35 years old, two cleavage stage embryo transfer was performed, and single blastocyst transfer is performed for all blastocyst transfer cycles.
3.2. Luteal phase support regimen: The luteal phase support starts from the day 2 after oocyte retrieval day. Oral dydrogesterone 30mg daily or vaginal progesterone gel 90mg combined with oral Dydrogesterone 20 mg was administrated for luteal phase support.
3.3. Outcome measures: 14 days after cleavage-stage embryo transfer and 12 days after blastocyst transfer, the positive result of serum β-HCG level was considered as biochemical pregnancy; 2 weeks and 4 weeks later, the ultrasound was performed. The normal gestational sac was considered as clinical pregnancy. Clinical pregnancy rate and live birth rate were followed up. Miscarriage was defined if the clinical pregnancy was lost spontaneously before 28 weeks of gestation. Implantation rate was defined as the ratios of the gestational sac number over the transferred embryo number.
4.statistical analysis
4.1 SPSS27.0 software was used for statistical processing, and the results were expressed as Median (25th percentile, 75th percentile) or percentage (%). The mean values of the two groups of samples were compared using Mann-Whitney U test, each as appropriate and the ratios were compared using Chi-square test. Value of p < 0.05 was considered statistically significant.
4.2 Propensity score matching was carried out to adjust for numerical differences and to balance between the two groups. The matching parameters were the woman's age, years of infertility, the woman's BMI, the total number of eggs retrieved, the serum level of FSH、LH、E、P、PRL、T level , the total dosage of Gn and AFC, with a matching tolerance of 0.02, and non-repetitive sampling at a ratio of 1:1.