比較（A）黃體素補充 &注射促排卵後第 6 天（第 0 天）進行移植；（B）黃體素補充 &促排卵後第 7 天進行 LPS 注射移植；（C）不黃體素補充&促排卵後第 6 天進進行移植；（D）不黃體素補充 &促排卵後第 7 天進行移植--------- 四組活產率無明顯差異

黃體素補充與否 & 注射促排卵後第 6 天或第7天對活產率無明顯影響

. 2026 Jan 13;2026(1):hoag003.

 doi: 10.1093/hropen/hoag003. eCollection 2026.

Optimizing the protocol for modified natural cycle frozen embryo transfer (mNC-FET): a multicentre, single-blinded randomized controlled trial

Study question: Can the use of progesterone luteal phase support (LPS) and timing of blastocyst transfer, at 6 versus 7 days following hCG-trigger, improve the live birth rate (LBR) in modified natural cycle (mNC) frozen-thawed embryo transfer (FET)?

Summary answer: Use of LPS and advanced timing of blastocyst transfer did not significantly improve the LBR in mNC-FET.

What is known already: Transfer of a frozen-thawed blastocyst in the mNC protocol is routinely conducted 7 days after the ovulation trigger, and progesterone LPS is commonly used despite limited evidence.

Study design size duration: This multicentre, single-blinded, randomized controlled superiority trial investigated the effect of LPS and timing of blastocyst transfer on live birth rates following mNC-FET conducted from January 2019 to February 2024. Using an online randomization programme, patients were randomized 1:1:1:1 to: (A) transfer day 6 following ovulation trigger (Day 0) with LPS; (B) transfer day 7 with LPS; (C) transfer day 6 without LPS; (D) transfer day 7 without LPS. Use of LPS was masked from treating clinicians. The sample size calculation required 604 women to participate to detect an increase in live birth rate from 21% in control groups (LPS: C + D, timing: B + D) to 31% in intervention groups (LPS: A + B, timing: A + C). In total, 679 women were enrolled, and 610 women were randomized. Ultimately, 602 women (A: n = 151; B: n = 150; C: n = 149; D: n = 152) were included in the per-transfer analyses.

Participants/materials setting methods: Participants were women aged 18-41 years undergoing mNC-FET with a single autologous good-quality blastocyst, from eight public fertility clinics at tertiary care centres across Denmark.

Main results and the role of chance: Our study found that use of LPS did not significantly affect the LBR compared with no LPS: 34.9% (105/301) versus 31.9% (96/301) (adjusted risk difference (aRD) 3.18, 95% CI: -4.13 to 10.49; P = 0.39). Comparing blastocyst transfer on Day 6 versus Day 7, there was again no significant difference in LBR: 33.8% (99/300) versus 33.0% (99/302) (aRD -0.62, 95% CI: -7.99 to 6.75; P = 0.87).