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.
Blastocyst (day 5) embryos
In a 2025 meta-analysis, day 5 blastocysts were linked to higher pregnancy and live birth rates than day 6 blastocysts, while newborn outcomes were similar and poor quality day 5 embryos showed comparable potential to good quality day 6 embryos.
This post summarizes the 2025 ESHRE/ALPHA Istanbul consensus on egg and embryo assessment, offering patients a clear overview of how embryologists evaluate and rank eggs, zygotes, and embryos based on updated international guidelines.
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 day 7 euploids have the lowest ongoing pregnancy rate, when compared to day 5 and 6 euploids. These embryos were mostly poor quality.
Researchers in a 2023 study show that poor quality embryos have acceptable live birth rates compared to good and fair quality embryos, with only a slight increase in pregnancy loss and no differences in perinatal outcomes.
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 embryos that take longer to develop had lower quality scores for both the ICM and trophectoderm, and had reduced clinical pregnancy and live birth rates.
Researchers in a 2023 study combined the results of 74 studies to investigate what factors contribute to euploid live birth and miscarriage rates, identifying embryo quality, maternal age, specific diagnoses, repeat freeze/thaw, and other factors.
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 2023 study found comparable pregnancy and neonatal outcomes when transferring a day 5 poor quality or a day 6 good quality embryo.
Researchers in a 2022 study performed a meta-analysis to combine the results of studies examining the transfer of a good and poor quality embryo together (vs one good quality embryo alone), and found no differences in pregnancy or live birth rates, but increases in the rate of multiples.
Researchers in a 2022 study showed that extending embryo culture to day 7 increases the number of useable blastocysts, particularly for older women.
