FET programs still favor HRT despite safety concerns — but AI-backed hormone tracking may remove key barriers
70% Still Use HRT Despite 1.8x Higher Preeclampsia Risk
Over 70% of FET cycles in many programs still rely on programmed protocols, even though the absence of a corpus luteum in HRT cycles is associated with up to a 1.8-fold increased risk of preeclampsia and greater postpartum hemorrhage. While more predictable, HRT cycles come with a heavy medication burden—up to 10 weeks of estrogen and progesterone—and frequent patient-reported side effects.
Unscheduled Ovulation Makes Labs Work 7 Days a Week
Natural FET cycles remain clinically underused due to operational headaches. Unpredictable ovulation timing requires seven-day embryology lab availability and leads to more monitoring visits, more bloodwork, and more cancellations. Inconsistent LH surge definitions add further variability, increasing risk for missed or poorly timed transfers.
AI Predicts Ovulation with 95% Accuracy in 2.4 Visits
New machine learning tools are helping reduce these pain points. FertilAI, a platform trained on standard hormone blood tests, analyzes LH, estradiol, and progesterone levels to detect ovulation with 95% accuracy. A retrospective analysis of 515 NC-FET cycles found that aligning transfer timing with the AI model’s prediction resulted in a 9% increase in clinical pregnancy rates, while reducing the number of monitoring visits to just 2.4 per cycle—down from the typical 3.5 to 4
38% Fewer Weekend Transfers Lighten Lab Load
In clinics with limited weekend staffing, ovulation-triggered scheduling poses a serious constraint. In one setting where Sunday was closed and Saturday minimally staffed, FertilAI’s predictions reduced Sunday transfers to just 1.7% and shifted many Saturday cases to Friday. Overall, approximately 38% of cycles that would have landed on weekend days were rescheduled to weekdays
New Models Challenge the Programmed Cycle Default
Meta-analyses and registry data suggest natural or modified cycles may improve live birth rates and reduce hypertensive disorders. With trials like NatPro underway and AI tools easing scheduling pressure, the balance may shift. But for now, the main obstacle to NC-FET isn’t clinical—it’s operational.