Researchers in a 2026 study found that patients with only one fertilized egg (zygote) may have a higher chance of live birth with cleavage stage transfer than blastocyst stage transfer, especially at older ages.
Day 3 vs Day 5 embryo transfer
A 2025 meta-analysis combined 151 studies on interventions for advanced maternal age (>35) patients. It found no clear advantage to any specific stimulation protocol or FSH type, no benefit from routine ICSI, and decreased live birth with assisted hatching, while more research is needed on blastocyst versus cleavage-stage transfer and on PGT-A with modern methods.
A 2024 study found that beta-hCG levels were related to day 3 and day 5 embryo quality and development, with blastocyst expansion having the strongest impact on both initial beta values and their doubling.
A 2024 study compared IVF outcomes and pregnancy rates for patients of different ages (<32 to >40) who had their first single embryo transfer.
A 2024 study compared outcomes of IVF cycles that transferred day 2/3 or day 5/6 embryos, finding that day 2/3 embryos have higher live birth rates per cycle, particularly for patients with 3 or less embryos.
Researchers in a 2023 study found that live birth rates depend on a blastocyst’s grade, and not their day 3 grade, while miscarriage rates were affected due to day 3 cell number.
Researchers in a 2023 study found that probiotic supplementation had no impact on positive hCG pregnancy rates, but may improve miscarriage rates.
Researchers in their 2022 Cochrane review, performed a meta-analysis and combined the results of 32 studies that compared pregnancy outcomes of blastocyst and cleavage stage embryos, and found that blastocysts tend to produce better outcomes.
Researchers in a 2021 study analyzed nearly 100,000 FETs from the US SART registry and found that blastocyst stage transfers were slightly more likely to result in male live births than cleavage stage transfers.
Not sure what your embryo grade means—or if it affects your chances of success? This guide walks you through everything from day 3 and day 5 grading systems to what each number and letter combo (like 3BB or 5AA) actually means. You’ll also find success rate research, embryo photos, and insights from a former embryologist to help make sense of your report.