Comparison of embryo quality and pregnancy outcomes for patients with low ovarian reserve in natural cycles and mildly stimulated cycles: a cohort study

Abstract

Background

As women with low ovarian reserve embark on the challenging journey of in-vitro fertilisation (IVF) treatment, the choice between natural and mildly stimulated cycles becomes a pivotal consideration. It is unclear which of these two regimens is superior for women with low ovarian reserve. Our study aims to assess the impact of natural cycles on embryo quality and pregnancy outcomes in women with low ovarian reserve undergoing IVF treatment compared to mildly stimulated cycles.

Methods

This retrospective study enrolled consecutive patients with low ovarian reserve who underwent IVF/intracytoplasmic sperm injection (ICSI) at Guangdong Second Provincial General Hospital between January 2017 and April 2021. The primary outcome for pregnancy rate of 478 natural cycles and 448 mild stimulated cycles was compared. Secondary outcomes included embryo quality and oocyte retrieval time of natural cycles.

Results

The pregnancy rate in the natural cycle group was significantly higher than that in the mildly stimulated cycle group (51.8% vs. 40.1%, p = 0.046). Moreover, natural cycles exhibited higher rates of available embryos (84.1% vs. 78.6%, p = 0.040), high-quality embryos (61.8% vs. 53.2%, p = 0.008), and utilisation of oocytes (73% vs. 65%, p = 0.001) compared to mildly stimulated cycles. Oocyte retrievals in natural cycles were predominantly performed between 7:00 and 19:00, with 94.9% occurring during this time frame. In natural cycles with high-quality embryos, 96.4% of oocyte retrievals were also conducted between 7:00 and 19:00.

Conclusion

Natural cycles with appropriately timed oocyte retrieval may present a valuable option for patients with low ovarian reserve.

PLAIN LANGUAGE SUMMARY

In the realm of in-vitro fertilisation (IVF) treatment, women with low ovarian reserve often face the crucial decision of opting for natural or mildly stimulated cycles. This retrospective study, conducted between January 2017 and April 2021 at Guangdong Second Provincial General Hospital, delves into the impact of these cycles on pregnancy outcomes. Examining 478 natural cycles and 448 mildly stimulated cycles, the study reveals a notably higher pregnancy rate in the natural cycle group (51.8% vs. 40.1%). Additionally, natural cycles demonstrated higher rates of available embryos, high-quality embryos, and oocyte utilisation compared to their mildly stimulated counterparts. The findings suggest that natural cycles, with proper oocyte retrieval timing, could be a favourable choice for those with low ovarian reserve seeking IVF treatment.

Keywords:

• Natural cycles
• mildly stimulated cycles
• low ovarian reserve
• oocyte retrieval time
• pregnancy rate

Ethical approval

The study received approval from the Medical Ethics Committee of Guangdong Second Provincial General Hospital on August 16th (2022-SZ-KY-006-01).

Informed Consent

Not applicable. The requirement for informed consent was waived by the Medical Ethics Committee of Guangdong Second Provincial General Hospital.

Disclosure statement

No potential conflict of interest was reported by the author(s). This study adhered to the principles outlined in the Declaration of Helsinki.

Data availability statement

The data that support the findings of this study are available on request from the corresponding author.

Additional information

Funding

The study was financially supported by the National Natural Science Foundation of China (No. 81971357) and the Hospital Youth Research Project Fund of Guangdong Second Provincial General Hospital (No. YQ2020-007).