To evaluate whether there were significant differences in the effects of constant (5%) versus sequential (5%-2%) oxygen concentration protocols in embryo culture on term live birth rates.

This study will be conducted in five centers including the Clinical Center of Reproductive Medicine, First Affiliated Hospital of Nanjing Medical Universit. 980 women who wish to undergo blastocyst transplantation will be included in the study.

The study data will be analyzed statistically.

While blastocyst transfer has been shown to improve live birth rates, concerns exist regarding potential telomere shortening in offspring, which is associated with premature aging and various health issues. Our previous study further explores the role of oxygen tension in telomere length regulation, identifying hypoxia-inducible factor 1α (Hif1α) degradation as a key factor. Based on these findings, the study proposes a prospective, randomized controlled clinical trial comparing constant (5%) versus sequential (5%-2%) oxygen concentration protocols in embryo culture to assess their impact on term live birth rates and offspring telomere length.

This study will be conducted in five centers including the Clinical Center of Reproductive Medicine, First Affiliated Hospital of Nanjing Medical Universit. 980 women who wish to undergo blastocyst transplantation will be included in the study.

Female infertile patients who consent to blastocyst transfer will be considered for inclusion in the study. Patients will be randomly assigned to a constant (5%) or sequential (5%-2%) oxygen concentration protocols in embryo culture. This study will record live birth rates, perinatal and perinatal complications, and offspring health status of women in both groups of embryo culture regimens to assess the effects of different embryo culture regimens on term live birth rates and offspring health.

Inclusion Criteria:

1. Female: age ≥20 and ≤40 years, male: age ≥20 and ≤50 years;
2. Proposed 1st or 2nd cycle of IVF or ICSI fertilization;
3. ≥ 4 transferable embryos at oocyte stage.

Exclusion Criteria:

1. Diagnosis of abnormal uterine cavity morphology (confirmed by 3D ultrasound or hysteroscopy), including uterine malformations (mediastinal uterus, unicornuate uterus, bicornuate uterus), submucosal uterine fibroids, or uterine adhesions;
2. Patients who are proposed to undergo IVM;
3. Patients who are proposed to undergo PGD/ PGS;
4. Patients with untreated severe hydrosalpinx (confirmed by ultrasound or HSG);
5. Patients with a history of recurrent miscarriage (2 or more previous pregnancy losses, excluding biochemical pregnancies);
6. Patients who plan to freeze whole embryos and are unable to complete a single embryo transfer within six months;
7. Patients with contraindications to assisted reproductive technology and pregnancy, or suffering from diseases that have a definite effect on pregnancy: including uncontrolled hypertension, heart disease with definite symptoms, uncontrolled diabetes, undefined diagnosis of liver or kidney disease or liver or kidney insufficiency, severe anemia, history of previous venous thrombosis, pulmonary embolism or cerebrovascular events, history of malignant tumors, suspected malignant tumors, and undiagnosed abnormal uterine bleeding.