Sean Lauber: Is a Day 3 or Day 5 Embryo Transfer Better?
Sean Lauber, Founder of Remembryo, shared on LinkedIn:
“Day 5 blastocysts have higher live birth rates per transfer than day 3 embryos. But does waiting until day 5 improve the overall chance of having a baby from an egg retrieval? That part isn’t really clear.
A 2026 meta-analysis combined four randomized trials with 2,432 patients. The chance of at least one live birth after transferring available embryos was 66.0% with day 5 vs 61.1% with day 3. The difference was borderline, and the researchers considered the results clinically comparable.
Another 2026 meta-analysis, a Cochrane Review, analyzed the evidence differently and found a small advantage with day 5 during the first year.
The problem is that most studies didn’t transfer every embryo. Clinics usually transferred the best blastocysts first, and many patients still had embryos left over when follow-up ended. This can make day 5 look better during the first few transfers without showing which strategy would produce more births if every embryo were given a chance.
The randomized trials mainly included good prognosis patients with multiple embryos. Other studies suggest embryo number may matter: with only one or a few embryos, day 3 may sometimes be the better choice.
Day 5 can reduce the number of unsuccessful transfers, but it also leaves fewer embryos available and increases the chance of having nothing to transfer.
There still isn’t one strategy proven best for every patient.
I’ve put together a new Evidence Guide covering the latest research and key questions about day 3 vs day 5 embryo transfers.
Check out more details on Remembryo.
Like this post? Get a free weekly summary of the latest IVF research.”
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