Reproductive healthLecture
Endometrial preparation for frozen embryo transfer
HRT, modified natural or true natural cycle — which preparation actually delivers the best obstetric outcomes? A practical synthesis of recent data on E2 duration, progesterone route and timing, day-of-transfer monitoring, and the new NPP protocol that may reshape weekend scheduling.
Audio: MultiSubtitles: EN · UA · RU37 min
Christophe Blockeel
Professor, MD, PhD
Reproductive endocrinologist and gynecologist, and Medical Director of Brussels IVF — the Centre for Reproductive Medicine at University Hospital Brussels (UZ Brussel). Professor at the Vrije Universiteit Brussel and visiting professor at the University of Zagreb, with more than 20 years in reproductive medicine. His work focuses on ovarian stimulation, embryo transfer and assisted reproductive technologies, with more than 300 scientific publications.
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What was shown
Frozen embryo transfer is now the dominant first-line procedure in ART. The talk compares HRT, modified natural and true natural cycles, examines E2 duration, day of progesterone before transfer, day-of-transfer progesterone monitoring, and the NPP protocol — a natural-cycle scheduling tool that uses vaginal progesterone instead of an HCG trigger.
Key findings
HRT cycles are associated with significantly more preeclampsia, hypertensive disorders, postpartum haemorrhage and preterm birth than natural cycles. E2 preparation should not exceed 28 days; under 8-10 days is associated with worse outcomes. Day 5, 6 and 7 of progesterone before blastocyst transfer all give comparable pregnancy rates, with day 6 now adopted as standard. Day-of-transfer serum progesterone below 8.8-9.2 ng/mL is associated with significantly lower live birth, and adding a second route (subcutaneous progesterone or oral dydrogesterone) normalises outcomes.
