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. 2025 Jun;42(6):1805-1812.
doi: 10.1007/s10815-025-03459-9. Epub 2025 Mar 29.

Impact of low versus high oxygen tension on human oocyte maturation during biphasic capacitation IVM (CAPA-IVM)

Huy H Pham  1   2 , Viet Q Tran  3   4 , Anh H Le  3   4 , Duy L Nguyen  4 , Toan D Pham  4 , Anh L Vu  4 , Tien K Le  3   4 , Ho L Le  3   4 , Bao G Huynh  5   4 , Tuong M Ho  5   4 , Lan N Vuong  6
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Impact of low versus high oxygen tension on human oocyte maturation during biphasic capacitation IVM (CAPA-IVM)

Huy H Pham et al. J Assist Reprod Genet. 2025 Jun.

Abstract

Purpose: This study investigated the impact of low versus high oxygen tension on the oocyte maturation rate in biphasic CAPA-IVM.

Methods: A sibling oocyte pilot study of cumulus-oocyte complexes (COCs) from participants with polycystic ovary syndrome was performed at an academic IVF center in Vietnam from November 2023 to May 2024. At collection, COCs were allocated to undergo CAPA-IVM culture with low oxygen tension (5%) or high oxygen tension (20%). Culture of COCs took place in two benchtop incubators, each equipped with commercial mix-gas bottles to establish the respective oxygen conditions. The primary outcome was the oocyte maturation rate. Secondary outcomes were rates of two-pronuclei fertilization, day-3 embryos, blastocyst formation, and good-quality embryos.

Results: A total of 554 COCs from 20 participants were assigned to the low oxygen (276 COCs) or high oxygen (278 COCs) tension groups. The oocyte maturation rate was significantly lower in the low oxygen tension versus high oxygen tension group (53.6% vs. 65.8%, risk ratio 0.81, 95% confidence interval 0.71-0.94; p=0.004). The two-pronuclei fertilization rate was significantly lower in the low oxygen tension versus high oxygen tension group (61.5% vs. 72.7%, p=0.03). Numbers of day-3 embryos, blastocysts, and good-quality blastocysts were slightly, but not significantly, lower in the low oxygen tension group compared with the high oxygen tension group.

Conclusions: Low oxygen tension of 5% during both steps of biphasic CAPA-IVM reduced the number of matured oocytes and 2-pronuclei fertilized oocytes compared with the use of high oxygen tension (20%) during CAPA-IVM.

Keywords: CAPA-IVM; Cumulus-oocyte complex; in vitro maturation; High oxygen tension; Low oxygen tension.

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Conflict of interest statement

Declarations. Competing interests: Lan N Vuong has received speaker and conference fees from Merck; and grant, speaker, and conference fees from Merck Sharpe & Dohme and Ferring. Tuong M Ho has received speaker fees from Merck, Merck Sharp & Dohme, and Ferring. Other authors have no financial relationships with any organizations that might have an interest in the submitted work in the previous 3 years and no other relationships or activities that could appear to have influenced the submitted work.

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