Comparable Clinical and Embryological Outcomes in Luteal and Follicular Phase Controlled Ovarian Hyperstimulation: A Retrospective Cohort Study.

OBJECTIVE

To study whether luteal phase stimulation provides clinical and embryological outcomes comparable to follicular phase stimulation in controlled ovarian hyperstimulation cycles.

DESIGN

Retrospective cohort study.

SUBJECTS: A total of 12,442 patients undergoing 18,062 in vitro fertilization cycles between January 1, 2018, and December 21, 2021, across 6 assisted reproductive technology centers within a large US fertility network.

EXPOSURE: Patients underwent controlled ovarian hyperstimulation using either follicular phase or luteal phase initiation. Cycles involving fresh transfers, day 3 transfers, or poor endometrial receptivity were excluded.

MAIN OUTCOME MEASURES: The primary outcomes were clinical pregnancy rates and cumulative live birth rates. The secondary outcomes included the number of oocytes retrieved, oocyte maturation rate, fertilization rate, blastocyst biopsy rate, and euploid embryo rate.

RESULTS

The clinical pregnancy rates were similar between follicular (68.44%) and luteal (67.67%) phase stimulations (odds ratio, 0.975; 95% confidence interval [CI], 0.751-1.266). Luteal phase stimulation required a higher total follicle-stimulating hormone dose (4,350.92 IU vs. 3,989.11 IU); however, stimulation duration did not differ significantly. Follicular phase stimulation yielded more oocytes on average (12.61 vs. 11.85), although luteal phase stimulation produced more oocytes in paired analyses (8.54 vs. 7.31). Among patients aged <35 years, the blastocyst biopsy rates were higher in luteal cycles (61.01% vs. 55.37%). No significant differences were found in the oocyte maturation, fertilization, or euploid embryo rates. The cumulative live birth rates were comparable across age groups and transfer attempts.

CONCLUSION

Luteal phase stimulation offers clinical and embryological outcomes comparable to follicular phase stimulation in in vitro fertilization. In patients aged <35 years, it may provide higher blastocyst biopsy rates, supporting its use as a flexible and effective stimulation option.