Assisted reproduction technology (ART) is the main method for addressing infertility and attaining pregnancy. Although age is typically acknowledged as the primary determinant of ART success, the cause of infertility and the specific ART treatments employed can also impact pregnancy outcomes. Recent study examined the impact of natural cycles compared to mildly stimulated cycles on embryo quality and pregnancy outcomes for women with low ovarian reserve undergoing IVF treatment. The researchers conducted a retrospective cohort study of 926 cycles at the Guangdong Second Provincial General Hospital between 2017-2021.

Embryo Quality and Pregnancy Rates
The results showed that the pregnancy rate was significantly higher in the natural cycle group compared to the mildly stimulated cycle group (51.8% vs. 40.1%). Natural cycles also had higher rates of available embryos (84.1% vs. 78.6%), high-quality embryos (61.8% vs. 53.2%), and utilization of oocytes (73% vs. 65%) compared to mildly stimulated cycles.
Timing of Oocyte Retrievals
Importantly, the majority of oocyte retrievals in natural cycles (94.9%) were conducted during daytime hours (7am-7pm), with an even higher percentage (96.4%) in cycles that resulted in high-quality embryos. This suggests that natural cycles with appropriately timed oocyte retrieval may be a valuable option for patients with low ovarian reserve.
Conclusions and Recommendations
The researchers conclude that natural cycles can yield significantly higher pregnancy rates, higher rates of available and high-quality embryos, and better utilization of oocytes compared to mildly stimulated cycles in women with low ovarian reserve. These findings indicate that natural cycles with properly scheduled oocyte retrieval may be a beneficial approach for this patient population.

Key Points
1. The study examined the impact of natural cycles compared to mildly stimulated cycles on embryo quality and pregnancy outcomes for women with low ovarian reserve undergoing IVF treatment.
2. The pregnancy rate was significantly higher in the natural cycle group compared to the mildly stimulated cycle group (51.8% vs. 40.1%).
3. Natural cycles had higher rates of available embryos (84.1% vs. 78.6%), high-quality embryos (61.8% vs. 53.2%), and utilization of oocytes (73% vs. 65%) compared to mildly stimulated cycles.
4. The majority of oocyte retrievals in natural cycles (94.9%) were conducted during daytime hours (7am-7pm), with an even higher percentage (96.4%) in cycles that resulted in high-quality embryos.
5. The researchers conclude that natural cycles can yield significantly higher pregnancy rates, higher rates of available and high-quality embryos, and better utilization of oocytes compared to mildly stimulated cycles in women with low ovarian reserve.
6. The findings indicate that natural cycles with properly scheduled oocyte retrieval may be a beneficial approach for women with low ovarian reserve undergoing IVF treatment.
Reference -
Rui-Ying Yuan, Sen Li, Xie Feng, Xiao-Long Li, Xiao-ting Lin, Fu-min Gao, Hai-Jing Zhu, Yong-shi Li, Yan-chu Li & Xiang-Hong Ou (2024) Comparison of embryo quality and pregnancy outcomes for patients with low ovarian reserve in natural cycles and mildly stimulated cycles: a cohort study, Journal of Obstetrics and Gynaecology, 44:1, 2303693, DOI:10.1080/01443615.2024.2303693