Su Y, Ji H, Jiang W, et al. - Researchers conducted a retrospective clinical study involving 2,256 artificial frozen-thawed embryo transfer (AC-FET) cycles with the aim to determine if and how unplanned spontaneous follicular growth and ovulation influence clinical outcomes after planned AC-FET cycles. Two groups were formed of the individuals: a study group: cycles with spontaneous follicular growth and ovulation (the maximum diameter of follicles in any ovary was ≥ 14 mm and ovulation was confirmed by consecutive ultrasound examinations) and a control group featuring cycles without growing follicles (the maximum diameter of follicles in both ovaries were < 10 mm). Findings revealed significant and positive association of patient age and basal FSH level with the spontaneous follicular growth and ovulation event. Further, they observed negative correlation of this event with BMI, AMH level and a high starting oestrogen dose. Outcomes revealed that AC-FET and spontaneous follicular growth and ovulation events led to retrieval of notably better pregnancy outcomes with a significantly greater implantation rate, clinical pregnancy rate, ongoing pregnancy rate and live birth rate and a significantly reduced miscarriage rate.