Ethical Approval
of the Study Protocol
The reproductive ethics committee of the Affiliated Hospital of Shandong University of Traditional Chinese Medicine (TCM) certified this study as ethical (Identifier: SDUTCM/2021.7.26). All patients provided written informed consent. All treatments were undertaken in strict accordance with the Declaration of Helsinki 1964 and its later amendments.
Study Design
This study was a registered randomized controlled trial (RCT, http://www.chictr.org.cn/, identifier: ChiCTR2100049292) carried out in the reproductive center, affiliated hospital of Shandong University of Traditional Chinese Medicine, between July 2021 to January 2023 (12).
Inclusion Criteria
(1) Patients with an expected normal ovarian response (NOR) who had no previous history of cancellation of an in vitro fertilization / intracytoplasmic sperm injection (IVF/ICSI) cycle and a poor ovarian response; 6 ≤ AFC ≤ 15; 1.2ng/ml ≤ AMH ≤ 3.5ng/ml; Basal FSH < 10 mIU / ml; (2) Patients with < 50% mature oocytes in the only one previous fresh IVF/ICSI cycle triggered with hCG; (3) In the previous IVF/ICSI cycle, standard ovarian stimulation protocol was performed using a GnRH-ant protocol.
Exclusion Criteria
(1) Age ≥ 40 years old ; (2) Patients with a body mass index (BMI) ≥ 30 kg/m2; (3) Individuals with high risk of OHSS during controlled ovarian stimulation; (4) Patients with endocrine or metabolic disorders; (5) Patients with untreated severe endometriosis, submucosal myoma, multiple endometrial polyps, pelvic inflammation, uterine malformation, Asherman syndrome and hydrosalpinx prior to embryo transfer (ET); (6) Patients with abnormal immune function and chromosome karyotype of either spouse.
Randomization and Blinding
Randomization was commenced on the trigger day. A random sequence of codes was used to assign individuals to one of two groups, A or B, in a 1:1 ratio by computer. A central randomization database was established to store the randomization scheme (www.medresman.org). The online randomization procedure was operated by a data specialist who was not involved in patient recruitment and clinical management. Physicians were informed by e-mail of the allocation results after randomization. As a result, the operation ensured that allocation concealment was maintained since the service did not reveal the allocation until after the randomization process, i.e., after the baseline visit. Considering the nature of the intervention, we did not blind physicians and participants to the intervention. However, the trial outcome assessors were blinded to the assigned groups.
Controlled Ovarian Stimulation Protocol
Standard ovarian stimulation protocol with gonadotrophins was performed using a GnRH-ant protocol. Ovarian stimulation with 150–225 IU/day of recombinant FSH (Puregon, Merck Sharp & Dohme B.V., Haarlem, Netherlands) was started on the 3rd day of the menstrual cycle. The patients' attending physicians determined the starting dose of Gn based on their age and BMI before participation in the study and dynamically monitor the ovarian response based on the results of serial transvaginal ultrasound follicle measurements and assays of serum E2, progesterone (P4), LH. The dose of Gn was adjusted according to the subject’s response. When ovarian stimulation reached the fifth day, GnRH-ant (0.25mg, Cetrorelix; Merck Serono, Darmstadt, Germany) was added and continued until trigger day. When 2 follicles were ≥ 18mm in diameter or when 3 follicles were ≥ 17mm in diameter, triggering was performed. According to the results of randomization, patients were divided into the following two groups: (1) hCG-only trigger: Patients were triggered with recombinant hCG (r-hCG, 6500 IU, Ovidrel, European Serono, France) 36 hours before OPU; (2) Dual trigger: Patients were triggered with co-administration of 0.2 mg GnRH-a (0.1mg, Diphereline, France, Epson) and hCG, 40 and 34 hours prior to OPU, respectively. Oocyte retrieval was performed by transvaginal puncture under transvaginal ultrasound guidance.
Embryo Culture
Cumulus cells were enzymatically removed from oocytes and mature oocytes were subjected to intracytoplasmic sperm injection. In an environment of 5.0% O2 and 5.6% CO2, the pre-equilibrated embryo Petri dishes were used to culture zoosperm. According to Gardner's criteria, embryo morphology and quality were evaluated. When selecting embryos for vitrification or transfer, it should focus on no fewer than six blastomeres with ≤ 20% fragmentation, which indicates top quality. Embryos with a fragmentation rate between 20% and 50% were not transferred or vitrified unless they reach the 8-cell stage on day 3. In our center, we have consistently adhered to the principle of transferring one top-quality day 3 embryo or two suboptimal embryos at the cleavage stage. Fresh embryo transfer would be cancelled if met: Endometrial thickness less than 7 mm on trigger day; Serum P4 levels greater than 1.5ng/ml on trigger day; High OHSS risk, i.e., retrieval of more than 15 oocytes and serum E2 concentrations higher than 4000 pg/ml on trigger day, etc.
Endometrial Preparation Protocol for FET
Transvaginal ultrasound and serum hormone measurements (LH, E2, and P4) were performed on days 8 through 10 of the menstrual cycle, depending on the duration of the menstrual cycle, to track endometrial thickness and follicle size until ovulation triggering conditions were reached. A single intramuscular injection of 4000 IU hCG (Lizhu Pharmaceutical Trading Co., China) was used to trigger ovulation when the dominant follicle diameter was more than 17 mm, the endometrial thickness was more than 7 mm, P4 was less than 1.5 ng/ml, and E2 was more than 150 pg/mL. At approximately 9:00 am, the hCG injection was administered. Patients who had unanticipated spontaneous ovulation while being monitored, as well as those who had no prominent follicles by day 25 of the menstrual cycle, were eliminated.
Luteal Phase Support Protocols
Routine luteal phase support was given after embryo transfer (ET), using intramuscular P4 (Zhejiang Xianju Pharmaceutical Co., Ltd.) injection 40mg/day, P4 vaginal sustained release gel (8% Crinone, Moxerano) 90mg/day, or oral P4 10mg three times a day (dydrogesterone, Abbott Laboratories biologicals), or in combination, continued from the day of ET until 10 weeks of gestation. The manner of P4 administration is determined by the clinical preferences of both physicians and patients.
Study Endpoints and Definitions
The primary outcome was oocytes maturation rate (i.e., the percentage of the number of MII oocytes over the total number of oocytes retrieved).
The secondary outcomes are number of oocytes retrieved, normal fertilization rate (the proportion of oocytes that become fertilized), number of two-pronuclear (2PN) embryos, number of D3 top quality embryos (TQE), number of D3 transferable embryos, number of remaining frozen embryos, cumulative clinical pregnancy rate and cumulative live birth rate (LBR). Top quality embryo was defined as seven or more blastomeres of uniform size and fragmentation rate less than 20% on day three. Clinical pregnancy was defined as the appearance of a gestational sac and fetal heartbeat detected by transvaginal ultrasonography. Cumulative clinical pregnancy rate and LBR were defined as the proportion of participants with clinical pregnancy or live birth after one year of follow-up.
Data Statistical Analysis
This clinical study was a superiority, randomized parallel controlled trial. The primary outcome measurement was MII oocytes rate. According to previous data of our center, the mean estimated rate of MII oocytes in dual trigger group was approximately 70%, using GnRH-a (40h before OPU) + hCG (34h before OPU), and 30% in hCG trigger group, with standard deviations of 40% for each group. The sample size of 40 individuals for each group was calculated by PASS 15.0 (NCSS, LLC. Kaysville, Utah, USA.) assuming α = 0.05 (two-sided) and β = 0.10 (90% power). Suppose that a dropout rate of 10%, we calculated that the sample size for each group was 45 individuals. Ultimately, the RCT need to recruit a total of 90 individuals.
Because the randomization was implemented on the trigger day, recruited participants who dropped out of trial during the ovarian stimulation process were not randomized. Therefore, only outcome variables were analyzed for subjects randomized to the study protocol (per protocol analysis). All the data were analyzed with SPSS version 26.0. Data are presented as mean ± standard deviation (Mean ± SD) for continuous variables and as frequency (percentage) [n (%)] for categorical data. According to the normality and variance of the data, the continuous data were analyzed by use of Student's t-test or Mann-Whitney U-test. When data did not conform to normal distribution, a nonparametric test was used, which were expressed as the median (interquartile range) [M (IQR)]. Categorical data were analyzed using chi square and Fisher's exact tests with an expected frequency of less than 5. P < 0.05 indicated that the difference was statistically significant.