Management of Early Follicle Recruitment in FET Cycles
When early follicle recruitment occurs during a frozen embryo transfer (FET) cycle, you should proceed with the transfer rather than cancel the cycle, as clinical outcomes remain comparable to cycles without follicular development.
Decision Algorithm Based on Follicle Size
Small Follicle Development (<14mm)
- Continue with the planned FET cycle without modification 1, 2
- Clinical pregnancy rates, live birth rates, and miscarriage rates show no significant differences compared to cycles without follicular development 1, 2
- This approach preserves valuable treatment cycles that would otherwise be unnecessarily cancelled 1
Large Follicle Development (≥14mm) Without Ovulation
- Proceed with transfer as planned 1
- Pregnancy rates remain comparable to cycles without dominant follicle development 1
- No significant difference in clinical outcomes justifies cycle cancellation 1
Documented Ovulation During HRT Cycle
- Exercise caution but consider proceeding 1
- Clinical pregnancy rates remain similar to non-ovulatory cycles 1
- Important caveat: Early miscarriage rates are significantly higher when ovulation occurs (compared to cycles without follicular development or with follicles that don't ovulate) 1, 2
- Counsel patients about the increased early pregnancy loss risk before proceeding 1
Clinical Monitoring Approach
Risk Factors for Unexpected Follicular Development
Monitor more closely in patients with: 2
- Older age (increased risk with each year)
- Lower antral follicle count (AFC)
- Lower anti-Müllerian hormone (AMH) levels
- Lower initial estrogen dosing
Practical Management
- Serial ultrasound monitoring during endometrial preparation identifies follicular development early 1, 2
- Document follicle size and whether ovulation has occurred before making transfer decisions 1
- The traditional concern about difficulty determining optimal transfer timing is not supported by clinical outcome data 1
Evidence Quality and Nuances
The strongest evidence comes from a retrospective cohort of 171 FET cycles specifically examining this question, demonstrating that dominant follicle development or ovulation is not a necessary indication to cancel transfer cycles 1. This is further supported by a larger propensity score-matched analysis of 7,064 cycles showing similar findings 2.
Common pitfall to avoid: Reflexively cancelling cycles when follicular development is detected, which wastes valuable embryos and delays treatment without improving outcomes 1. The only scenario requiring heightened caution is documented ovulation, where increased early miscarriage risk should inform patient counseling 1, 2.