Single Embryo Transfer Now Outperforms Multiples: What the New Data Means for You

For years, transferring two or three embryos at once felt like the "safer" bet — more embryos, more chances, right? A major new study says otherwise. Modern single embryo transfer (SET) now delivers success rates that rival or beat older multiple-transfer approaches, with a fraction of the health risk. Here's what changed, and what it means for your own protocol conversation with your RE.

The New Data

The study, led by researcher D. Morbeck and colleagues, was presented at the 42nd Annual Meeting of the European Society of Human Reproduction and Embryology (ESHRE) and published in the journal Human Reproduction. Researchers analyzed outcomes from 18,396 women undergoing their first IVF cycle between 2012 and 2021 across seven Australian fertility clinics, with follow-up through the end of 2023 — making it one of the largest studies of its kind.

Compare that to outcomes from before modern lab techniques became standard: three-cycle cumulative live birth rates around 53–59%, with multiple pregnancy rates often exceeding 20%. In plain terms — today's patients are getting better odds of taking home a baby while dramatically reducing the risk of a twin or triplet pregnancy, which carries higher rates of preterm birth, low birth weight, and NICU stays.

Why Single Embryo Transfer Became Viable

Researchers attribute the improved outcomes to these combined advances rather than any single breakthrough. As one ESHRE leader put it in the study's press materials, modern IVF gains tend to come from steady, incremental improvements in laboratory practice rather than dramatic leaps — but the cumulative effect has been substantial.

Why This Matters for Your Health, Not Just Your Odds

Separate research has found that single embryo transfer also reduces the risk of infant death within the first month of life compared to multiple embryo transfer — a risk driven largely by the complications associated with twin and triplet pregnancies. For decades, patients were sometimes implicitly asked to trade a small increase in per-transfer odds for meaningfully higher medical risk. That trade-off is shrinking fast.

Are There Still Cases Where Multiple Transfer Makes Sense?

Yes — this isn't a one-size-fits-all rule. Your RE might still discuss transferring more than one embryo if:

• You're 38 or older and have limited embryos of uncertain quality
• You've had multiple prior failed single transfers with genetically normal embryos
• You have a specific diagnosis where embryo quality assessment is less reliable

Even in these situations, most reproductive endocrinologists today start the conversation from a single-embryo default and discuss multiples only when the individual case supports it — a shift from a decade ago when the reverse was often true.

The best outcome isn't the highest odds on any one transfer — it's the healthiest pregnancy across your whole treatment plan.

Questions to Ask Your RE

• "What's my clinic's single-embryo transfer rate, and how does it compare to the national average?"
• "Based on my embryo quality and age, what's my estimated cumulative live birth rate across all my embryos?"
• "Would genetic testing (PGT-A) change your recommendation on how many embryos to transfer?"