Constant 5% versus sequential 5% to 2% oxygen for embryo culture in IVF

A Multicenter Prospective Randomized Controlled Clinical Trial Comparing Constant (5%) Versus Sequential (5%-2%) Oxygen Concentration Embryo Culture Protocols in Assisted Reproductive Technology: Evaluating Term Live Birth and Offspring Health Outcomes

This will test whether keeping embryos at a constant 5% oxygen level or lowering oxygen from 5% to 2% during culture changes term live birth rates for women undergoing blastocyst IVF.

Quick facts

• Phase: Not applicable
• Study type: Interventional
• Enrollment: 980 (estimated)
• Ages: 20 Years to 40 Years
• Sex: Female
• Sponsor: The First Affiliated Hospital with Nanjing Medical University (Academic / other)
• Locations: 5 sites (Zhengzhou, Henan and 4 other locations)
• Trial ID: NCT07050537 on ClinicalTrials.gov

What this trial studies

In a multicenter, randomized controlled design, about 980 women planning blastocyst transfer will be assigned to embryo culture under either a constant 5% oxygen environment or a sequential 5%→2% oxygen protocol. The trial will be conducted at five Chinese reproductive centers using standard IVF/ICSI procedures with random allocation at the embryo culture stage. Primary outcome is term live birth rate, and secondary outcomes include perinatal complications and offspring telomere length and health measures. All data will be analyzed statistically to compare clinical and offspring outcomes between the two oxygen regimens.

Who should consider this trial

Good fit: Women aged 20–40 undergoing their first or second IVF/ICSI cycle who produce at least four transferable oocytes and plan blastocyst transfer are ideal candidates.

Not a fit: Patients with uterine anatomical abnormalities, plans for IVM or PGD/PGS, untreated severe hydrosalpinx, a history of recurrent miscarriage, or those freezing all embryos without completing a single transfer within six months are unlikely to benefit from this protocol comparison.

Why it matters

Potential benefit: If successful, the preferred oxygen protocol could increase term live birth rates and help preserve offspring telomere length, potentially improving long-term child health.

How similar studies have performed: Laboratory and some clinical work suggest low-oxygen (≈5%) culture improves embryo development and pregnancy outcomes versus atmospheric oxygen, but randomized data directly comparing constant 5% to sequential 5%→2% culture and effects on offspring telomere length are limited.

Eligibility criteria

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.

Where this trial is running

Zhengzhou, Henan and 4 other locations

• The Third Affiliated Hospital of Zhengzhou University — Zhengzhou, Henan, China (Recruiting)
• Changzhou Maternal And Child Health Care Hospital — Changzhou, Jiangsu, China (Recruiting)
• Nanjing Women and Children's Healthcare Hospital — Nanjing, Jiangsu, China (Recruiting)
• Reproductive Medicine of First Affiliated Hospital with Nanjing Medical University — Nanjing, Jiangsu, China (Recruiting)
• Suzhou Municipal Hospital — Suzhou, Jiangsu, China (Recruiting)

Study contacts

• Study coordinator: Xiang Ma

Conditions Fertility Issues; Blastocyst IVF; Embryo Culture; Fertility