Optimizing Donor Cycle Outcomes: Assessing the Efficacy of a Modified Warming Protocol for Vitrified Eggs

2024 Taiwan Society for Reproductive Medicine Annual Conference Prize Paper Presentation (Clinical Science)

Chien-Hong Chen*¹, Hsiu-Hui Chen¹, Shu-Hui Lin¹, Chun-Chia Huang¹, Chun-I Lee^1,2,3,
Pin-YaoLin¹, Tsung-Hsien Lee^1,2,3, Maw-Sheng Lee^1,2,3
Division of Infertility, Lee Women’s Hospital [1] Department of Obstetrics and Gynecology, Chung-Shan Medical University Hospital [2] Institute of Medicine, Chung Shan Medical University [3]
 

Study Question

Is there a correlation between the modified warming protocol and embryo developmental potential when using vitrified donor oocytes?
 

Study Design, Size, Duration

A retrospective cohort study was conducted at Lee Women’s Hospital, enrolling patients who underwent donation cycles with either fresh or vitrified oocytes between January 2019 and April 2024 (IRB: CS2-24096). The study included patients using vitrified donor oocytes (VDOs) with a conventional warming protocol (CWP, n = 408), VDOs with a modified warming protocol (MWP, n = 44), or fresh donor oocytes (FDOs, n = 174).

Materials, Setting, Methods

This study compared the efficacy of two warming protocols, i.e., CWP and MWP, for VDOs versus FDOs. The vitrification was performed using the CryoTech method (Reprolife, Japan). In the CWP, VDOs were treated in a three-step process, including 2 minutes in thawing solution (TS) at 37°C, 2 minutes in dilution solution (DS) at 25°C, and 5 minutes in washing solution (WS) at 25°C. In the MWP, the VDOs were treated in a simplified two-step process (TS and DS at 37°C for 2 minutes, respectively). The oocytes were then washed thoroughly in WS and transferred back to human tubal fluid (HTF) medium. The primary outcomes measured were survival rates (SR) after warming and blastocyst formation rates (BR) after intracytoplasmic sperm injection (ICSI). Statistical analyses used included generalized estimating equations, Fisher’s exact test, and chi-square tests.

Main Results

The oocytes were collected from donors aged 25.4 ± 2.7 years with a body mass index of 21.5 ± 2.9 kg/m2. Following the warming of VDOs, survival rates were found to be similar between the CWP group (93.7%, 7967/8506) and the MWP group
(93.9%, 920/980) (P > 0.05). The ICSI degeneration rates for VDOs (2.7%–3.4%) were comparable to that for FDOs (2.8%, 60/2106). Although the fertilization rates for VDOs (88.6%–89.7%) were significantly higher than those for FDOs (78.2%) (P < 0.05), abnormal fertilization rates, including 1 pronucleus and ≥ 3 pronuclei, were significantly higher in VDOs (9.1%–10.1%) compared to FDOs (3.2%). Based on normally fertilized embryos, the blastocyst formation rate for VDOs with CWP (57.5%, 3645/6337) was significantly lower than that for VDOs with MWP (77.3%, 566/732) and FDOs (67.2%, 1881/2799). Notably, the day 5 good blastocyst rate of VDOs was improved in the MWP group (27.3%, 200/732) compared to the CWP group (17.2%, 1091/6337) (P < 0.05).

Conclusion

This study demonstrates that the blastocyst development potential of VDOs using the MWP is improved to be comparable to that of FDOs. This suggests that MWP may serve as a standard protocol, potentially replacing the CWP.