A groundbreaking clinical trial has demonstrated that fresh embryo transfers yield superior outcomes compared to frozen embryos for women with low prognosis in in vitro fertilization (IVF) treatments, potentially reshaping current fertility treatment protocols.
The research, published in The BMJ on January 29, revealed that fresh embryo transfers resulted in a 40% live birth rate, significantly higher than the 32% achieved with frozen embryos. The study also showed higher overall pregnancy rates with fresh transfers at 47% compared to 39% for frozen embryos.
Clinical Trial Design and Outcomes
The multicenter study, conducted across nine fertility centers in China between December 2021 and May 2023, involved 838 women aged 33-34 who were classified as having low IVF prognosis due to factors such as age or egg quality issues. Participants were randomly assigned to either fresh or frozen embryo transfer groups, with outcomes monitored through April 2024.
Pregnancy loss rates showed a marked difference between the two approaches, with 31% in the frozen group experiencing losses compared to 23% in the fresh transfer group. Multiple birth rates also differed, with 9% of fresh transfer patients delivering twins versus 5% in the frozen group.
Implications for Current Practice
"Fresh embryo transfer may be a better choice for women with low prognosis in terms of live birth rate compared with a freeze-all strategy," stated the research team led by Professor Daimin Wei from Shandong University's State Key Laboratory of Reproductive Medicine and Offspring Health.
The findings challenge the current trend of routinely freezing all suitable embryos before transfer in low-prognosis cases. This practice has been particularly relevant as fertility clinics see increasing numbers of women with lower IVF success probability.
Safety and Additional Considerations
The study found no significant differences between the groups regarding birth weight, obstetric complications, or newborn health risks. However, experts from Radboud University, in an accompanying editorial, highlighted potential concerns about the freezing process itself.
"The process of freezing and thawing embryos is not without risks," noted Simone Cornelisse and colleagues. "Damage may occur during cryopreservation, storage, or thawing, and these steps can add substantial financial costs. Furthermore, treatment delays associated with elective freezing may be undesirable for some."
Future Research Directions
While these results are promising for patients with low IVF prognosis, researchers emphasize the need for additional studies to determine optimal protocols. Specifically, they recommend further investigation into the ideal number and developmental stage of embryos for fresh transfer in low-prognosis cases, particularly focusing on achieving singleton pregnancies.
Interestingly, the researchers noted that frozen embryo transfer continues to show better outcomes for women with good IVF prognosis, highlighting the importance of personalized treatment approaches in fertility care.
