A Prospective, Multicenter, Randomized Controlled Clinical Trial of an Undisturbed Embryo Culture System for Improving the In Vitro Developmental Potential of Embryos

This is a prospective, multicenter, randomized controlled clinical trial designed to evaluate whether a fully undisturbed closed embryo culture system can improve the developmental potential of embryos cultured in vitro and provide high-quality evidence for its clinical application. Participants must meet all of the following criteria to be eligible for this study: 1）Patients meeting the indications for IVF or ICSI; 2)No more than two previous IVF/ICSI embryo transfer cycles; 3) Willingness to culture all fertilized embryos to the blastocyst stage (Day 5/6); 4) AMH ≥1.2 ng/mL and AFC ≥7; 5) Fewer than 20 oocytes retrieved and serum estradiol level on the day of hCG administration <5000 pg/mL. Exclusion Criteria (Participants meeting any of the following criteria will be excluded): 1）History of low fertilization rate in previous cycles (fertilization rate <25%); 2）Oocyte donation or sperm donation cycles; 3）Either partner has a known chromosomal abnormality on karyotype analysis, or the couple plans to undergo preimplantation genetic testing (PGT); 4）Conditions that may affect oocyte quality, including premature ovarian insufficiency, endometriosis, ovarian endometrioma, or a history of two or more pelvic surgeries; 5）Requirement for surgical sperm retrieval, including microsurgical sperm retrieval or testicular sperm extraction; 6）Significant untreated uterine factors that may impair embryo implantation, including: submucosal uterine fibroids; two or more intramural fibroids, with the largest diameter ≥3 cm and significant compression of the uterine cavity causing cavity distortion; untreated moderate to severe intrauterine adhesions; one or more endometrial polyps with a maximum diameter ≥1.0 cm, or two or more space-occupying endometrial polyps within the uterine cavity; untreated moderate to severe hydrosalpinx (diameter ≥3 cm); 7）History of fertilization or oocyte maturation disorders, including fertilization failure in a previous ICSI cycle or previous oocyte maturation disorder. After ovarian stimulation, all cumulus-oocyte complexes (COCs) from each patient will be randomly allocated in a 1:1 ratio to the control group or the experimental group.In the control group, oocytes will be fertilized using Vitrolife fertilization medium and cultured in a conventional sequential culture system consisting of a benchtop incubator and sequential culture media. In the experimental group, oocytes will be fertilized using Gems FEM fertilization medium and cultured in an undisturbed system consisting of a Geri incubator and Gems one-step culture medium. After culture of all embryos to the blastocyst stage, a single best-quality blastocyst (better than 4BC) will be selected for transfer according to the Gardner morphological grading system, provided that patient interests are not compromised. The primary outcome is clinical pregnancy rate, defined as the proportion of clinical pregnancy cycles among all embryo transfer cycles. Clinical pregnancy will be assessed 4-7 weeks after embryo transfer by ultrasound detection of an intrauterine gestational sac or pathological confirmation of miscarriage tissue. Secondary outcomes include fertilization rate, normal fertilization rate after ICSI, cleavage rate, Day 3 good-quality embryo rate, Day 3 usable embryo rate, good-quality blastocyst formation rate, Day 5/6 usable blastocyst rate, blastocyst formation rate, implantation rate, biochemical pregnancy rate, early miscarriage rate, ongoing pregnancy rate, live birth rate.

Based on an average clinical pregnancy rate of 50%, and assuming a non-inferiority margin of 12% (Δ = -0.12), with α = 0.05, β = 0.20, 80% power, and 1:1 allocation, at least 430 cycles will be required. After allowing for a 10% dropout rate, a total of 478 cycles (239 per group) will be enrolled.

Participant recruitment is planned from November 1, 2025, to December 30, 2027, across the following 12 study centers: Center for Reproductive Medicine, The Sixth Affiliated Hospital, Sun Yat-sen University (leading center); Center for Reproductive Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology; Reproductive Center, Northwest Women's and Children's Hospital; Shenzhen Zhongshan Obstetrics and Gynecology Hospital; Assisted Reproduction Center, Jiangxi Maternal and Child Health Hospital; Center for Reproductive Medicine, West China Second University Hospital, Sichuan University; Center for Reproductive Medicine, General Hospital of Ningxia Medical University; Reproductive Center, Affiliated Hospital of Jining Medical University; Center for Reproductive Medicine, Nanjing Maternal and Child Health Care Hospital; Reproductive Center, Chenzhou First People's Hospital; Center for Reproductive Medicine, Changde First People's Hospital; and Center for Reproductive Medicine, The First Affiliated Hospital of Hainan Medical University.