title: The spatial arrangement of blastomeres at the 4-cell stage and IVF outcome.
abstract: This study compared the developmental and implantation potential of tetrahedrally arranged versus non-tetrahedrally arranged 4-cell-stage embryos. If the cleavage planes of a 4-cell-stage embryo were perpendicularly orientated, blastomeres were defined as tetrahedrally arranged, while embryos with parallel-orientated cleavage axes were considered as non-tetrahedral embryos. The 4-cell-stage embryos (n=862) examined in this study were obtained from 299 patients aged <36 years. A total of 299 embryos were transferred as a single-embryo transfer on day 3. This study showed that tetrahedral embryos developed into a 8-cell-stage embryo on day 3 more frequently (307, 45% versus 42, 24%; P<0.0001) and also developed more frequently into good-quality embryos (461, 67% versus 67, 38%; P<0.0001) and into excellent-quality embryos (290, 42% versus 34, 19%; P<0.0001). Tetrahedral embryos had a significantly higher implantation potential (98, 38% versus 9, 21%; P=0.038), ongoing pregnancy rate (84, 33% versus 7, 16%; P=0.032) and live birth rate (84, 33% versus 7, 16%; P=0.032). In conclusion, tetrahedral 4-cell-stage embryos on day 2 developed into embryos of better quality on day 3 with a higher implantation potential and live birth rate compared with non-tetrahedral 4-cell-stage embryos. In this study, an additional characteristic of 4-cell-stage embryos has been evaluated. The aim of the study was to evaluate the spatial arrangement of blastomeres in a 4-cell-stage embryo. If the cleavage planes of a 4-cell-stage embryo were perpendicularly orientated (indicating that both axes meet a right angle), blastomeres were defined as tetrahedral arranged while the other embryos were considered as non-tetrahedral embryos. The 4-cell-stage embryos (n=862) examined in this study were obtained from 299 patients aged <36 years. A total of 299 embryos were transferred as a single-embryo transfer on day 3. This study showed that tetrahedral embryos developed into an 8-cell-stage embryo on day 3 more frequently (307, 45% versus 42, 24%; P<0.0001) and also developed more frequently into good-quality embryos (461, 67% versus 67, 38%; P<0.0001) and excellent-quality embryos (290, 42% versus 34, 19%; P<0.0001). Tetrahedral embryos had a significantly higher implantation potential (98, 38% versus 9, 21%; P=0.038), ongoing pregnancy rate (84, 33% versus 7, 16%; P=0.032) and live birth rate (84, 33% versus 7, 16%; P=0.032). In conclusion, tetrahedral 4-cell-stage embryos on day 2 developed into embryos of better quality on day 3 with a higher implantation potential and live birth rate compared with non-tetrahedral 4-cell-stage embryos.
authors.affiliation: Leuven University Fertility Center, UZ Leuven, Gasthuisberg, Campus Gasthuisberg, Herestraat 49, 3000 Leuven, Belgium. Electronic address: goedele.paternot@uzleuven.be.
authors.forename: Goedele
authors.initials: G
authors.lastname: Paternot
authors.affiliation: Leuven University Fertility Center, UZ Leuven, Gasthuisberg, Campus Gasthuisberg, Herestraat 49, 3000 Leuven, Belgium. Electronic address: sophie.debrock@uzleuven.be.
authors.forename: Sophie
authors.initials: S
authors.lastname: Debrock
authors.affiliation: Leuven University Fertility Center, UZ Leuven, Gasthuisberg, Campus Gasthuisberg, Herestraat 49, 3000 Leuven, Belgium. Electronic address: diane.deneubourg@uzleuven.be.
authors.forename: Diane
authors.initials: D
authors.lastname: De Neubourg
authors.affiliation: Leuven University Fertility Center, UZ Leuven, Gasthuisberg, Campus Gasthuisberg, Herestraat 49, 3000 Leuven, Belgium. Electronic address: thomas.dhooghe@uzleuven.be.
authors.forename: Thomas M
authors.initials: TM
authors.lastname: D'Hooghe
authors.affiliation: Leuven University Fertility Center, UZ Leuven, Gasthuisberg, Campus Gasthuisberg, Herestraat 49, 3000 Leuven, Belgium. Electronic address: carl.spiessens@uzleuven.be.
authors.forename: Carl
authors.initials: C
authors.lastname: Spiessens
mesh_terms: D001757:Blastomeres / Q000166:cytology*; D002970:Cleavage Stage, Ovum / Q000166:cytology*; D047108:Embryonic Development / Q000502:physiology*; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D011247:Pregnancy; D011256:Pregnancy Outcome
keywords: 4-cell-stage embryos; IVF; embryo quality; embryo selection; live birth rate; spatial arrangement