Frozen transfers now represent 43 percent of all treatment cycles
Across 36 European nations in 2023, more than 1.15 million assisted reproduction cycles quietly produced 247,021 new lives — a testament to both the reach of modern fertility medicine and its ongoing refinement. The most telling shift is not in volume but in method: frozen embryo transfers have overtaken all other approaches combined, reflecting a deeper philosophical change in how clinicians think about timing, preparation, and the body's readiness. As twin and triplet births fall to historic lows and complication rates remain minimal, the data suggest that slower, more deliberate practice is yielding safer, more reliable outcomes. A new continent-wide registry now promises to carry this long tradition of careful observation into an era of even greater precision.
- Frozen embryo transfers have surpassed fresh IVF and ICSI cycles combined, signaling that the old model of immediate transfer is giving way to a more patient, strategic approach.
- With 401,483 frozen cycles recorded in a single year, the sheer scale of this shift is reshaping clinic workflows, patient timelines, and the economics of fertility care across Europe.
- Delivery rates for frozen transfers outperform fresh cycles — 27.6% versus 24.4% for IVF — giving clinicians and patients a compelling reason to embrace the slower path.
- Twin and triplet births have hit their lowest levels since monitoring began, as single-embryo transfer becomes standard practice and the risks of multiple pregnancies are deliberately reduced.
- The incoming EuMAR registry moves from pilot to permanent operation, promising cycle-by-cycle granularity that could finally close the gap between what clinics do and what researchers can measure.
In 2023, fertility clinics across 36 European countries reported more than 1.15 million assisted reproductive technology cycles, resulting in the birth of 247,021 children. The figures, drawn from 1,473 centers and presented at the European Society of Human Reproduction and Embryology's annual meeting, capture a field in the middle of a quiet but consequential transformation.
The defining trend is the rise of frozen embryo transfers. With 401,483 cycles performed, frozen transfers now account for 43 percent of all treatments — more than fresh IVF and ICSI cycles combined. The shift reflects a broader change in clinical philosophy: rather than creating and immediately transferring embryos, clinics increasingly preserve them, allowing time for genetic testing, uterine preparation, and more deliberate timing. The results support the approach. Frozen transfers achieved a delivery rate of 27.6 percent per transfer, outpacing fresh IVF at 24.4 percent and fresh ICSI at 23.5 percent.
Safety has improved alongside efficacy. Twin and triplet births have fallen to their lowest recorded levels, a direct consequence of the growing adoption of single-embryo transfer. Ovarian hyperstimulation syndrome occurred in just 0.18 percent of cycles, with bleeding and infection rates even lower. Four maternal deaths were recorded across the continent — a sobering figure, though the Consortium notes that underreporting remains a limitation across countries.
Europe's fertility infrastructure now substantially exceeds the global minimum threshold, averaging 2,547 ART cycles per million inhabitants against an estimated global need of 1,500. The European IVF Monitoring Consortium has tracked this field since 1997, documenting over 15.8 million cycles and 3.27 million births. Its successor, the EuMAR registry, is now moving toward permanent operation, designed to collect prospective, cycle-by-cycle data with greater depth — offering clinicians and policymakers a sharper lens through which to guide the next generation of reproductive medicine.
Across Europe, fertility medicine is undergoing a quiet but significant shift. In 2023, clinics reported more than 1.15 million assisted reproductive technology cycles—a staggering volume of treatment that resulted in the birth of 247,021 children. These numbers come from 1,473 fertility centers spread across 36 European countries, compiled by the European IVF Monitoring Consortium and presented at the 42nd annual meeting of the European Society of Human Reproduction and Embryology.
The most striking change in the data is the rise of frozen embryo transfers. Last year, clinics performed 401,483 frozen embryo transfer cycles—nearly as many as the 388,345 intracytoplasmic sperm injection cycles and far more than the 158,649 fresh in vitro fertilization cycles. When you add these three categories together, frozen transfers now represent 43 percent of all treatment cycles. This is not a marginal shift. It reflects a fundamental reorganization of how fertility clinics approach conception, moving away from the traditional model of creating and immediately transferring fresh embryos toward a system where embryos are preserved and used later.
Why does this matter? Frozen embryo transfer offers clinics and patients flexibility. It allows time for genetic testing, for uterine preparation, for spacing between cycles. The data suggest it works: delivery rates per embryo transfer reached 27.6 percent for frozen transfers, outpacing both fresh IVF at 24.4 percent and fresh ICSI at 23.5 percent. The shift has also coincided with a measurable improvement in safety. European clinics have reduced the number of embryos transferred during each cycle, a practice that has driven twin and triplet births to their lowest recorded levels since monitoring began. Multiple pregnancies carry real risks—for both mother and infants—so this trend toward single-embryo transfer represents a genuine advance in patient safety.
Complication rates remain low overall. Ovarian hyperstimulation syndrome, a potentially serious side effect of fertility drugs, occurred in just 0.18 percent of cycles. Bleeding was reported in 0.10 percent, infection in 0.02 percent. Four maternal deaths were recorded across the entire continent. The Consortium acknowledges, however, that these figures likely undercount the true incidence—not all complications are reported uniformly across countries.
The scale of European fertility treatment now substantially exceeds global need. Among countries with complete reporting, clinics performed an average of 2,547 ART cycles per million inhabitants, well above the estimated global minimum of 1,500 cycles per million population annually. This suggests that in much of Europe, access to fertility treatment is reasonably available, though access varies significantly by country and by wealth.
The European IVF Monitoring Consortium has been collecting this data since 1997, documenting more than 15.8 million treatment cycles and the births of over 3.27 million children. This continuity of data collection is rare globally and has allowed researchers and clinicians to track how practice evolves and how outcomes shift over decades. The next phase is already underway: ESHRE is developing a new registry called EuMAR—the European Monitoring of Medically Assisted Reproduction—designed to collect prospective, cycle-by-cycle data with even greater detail. After a successful pilot, EuMAR is moving toward permanent operation, promising to give clinicians, researchers, and policymakers an even clearer window into how fertility medicine is changing and where improvements can be made.
Citas Notables
The increase of frozen embryo transfer and continued reduction in multiple embryo transfers reflect a sustained commitment to improving both effectiveness and safety for patients.— Professor Diane De Neubourg, Chair of the EIM Consortium
Reliable, collaborative data collection remains essential for advancing reproductive medicine. The EIM registry enables clinics, researchers and policymakers to monitor long-term trends in treatment and outcomes, supporting evidence-based improvements in patient care across Europe.— Professor Dr Anis Feki, Chair of ESHRE
La Conversación del Hearth Otra perspectiva de la historia
Why has frozen embryo transfer grown so dramatically? What changed in the clinics?
It's partly technology—freezing and thawing embryos has become more reliable. But it's also strategy. Frozen transfer gives doctors time to test embryos genetically, to prepare the uterus, to space treatments. It turns out patients do better with that breathing room.
And the safety numbers—are those genuinely reassuring, or is there a reporting problem?
Both things are true. The rates we see are genuinely low. But the Consortium itself says complications are likely undercounted. Some clinics report meticulously; others don't. So the real picture is probably a bit worse than the numbers suggest, though still quite safe overall.
The shift to single embryos—that's driven by the data showing better outcomes?
Partly. But it's also driven by ethics and regulation. Multiple embryos mean multiple births, and those carry real risks for mothers and babies. Clinics realized they could get better results with one embryo than with two or three. That's a win on every front.
What does it mean that Europe is doing 2,500 cycles per million people when the global need is 1,500?
It means Europe has built capacity beyond what's strictly necessary. That's good—it suggests access is reasonably available. But it also masks huge variation. Some countries have abundant fertility clinics; others have almost none. The average hides the inequality.
Why does the new EuMAR registry matter if we already have 30 years of data?
Because the old data is retrospective—clinics report what happened after the fact. EuMAR will collect information in real time, cycle by cycle. That's more precise. It also means researchers can ask new questions and get answers faster. The field can adapt more quickly.