title: The Relationship between Cell Number, Division Behavior and Developmental Potential of Cleavage Stage Human Embryos: A Time-Lapse Study.
abstract: Day 3 cleavage embryo transfer is routine in many assisted reproductive technology centers today. Embryos are usually selected according to cell number, cell symmetry and fragmentation for transfer. Many studies have showed the relationship between cell number and embryo developmental potential. However, there is limited understanding of embryo division behavior and their association with embryo cell number and developmental potential. A retrospective and observational study was conducted to investigate how different division behaviors affect cell number and developmental potential of day 3 embryos by time-lapse imaging. Based on cell number at day 3, the embryos (from 104 IVF/intracytoplasmic sperm injection (ICSI) treatment cycles, n = 799) were classified as follows: less than 5 cells (< 5C; n = 111); 5-6 cells (5-6C; n = 97); 7-8 cells (7-8C; n = 442), 9-10 cells (9-10C; n = 107) and more than 10 cells (>10C; n = 42). Division behavior, morphokinetic parameters and blastocyst formation rate were analyzed in 5 groups of day 3 embryos with different cell numbers. In <5C and 5-6C embryos, fragmentation (FR; 62.2% and 30.9%, respectively) was the main cause for low cell number. The majority of 7-8C embryos exhibited obvious normal behaviors (NB; 85.7%) during development. However, the incidence of DC in 9-10C and >10C embryos increased compared to 7-8C embryos (45.8%, 33.3% vs. 11.1%, respectively). In ≥5C embryos, FR and DC significantly reduced developmental potential, whereas <5C embryos showed little potential irrespective of division behaviors. In NB embryos, the blastocyst formation rate increased with cell number from 7.4% (<5C) to 89.3% (>10C). In NB embryos, the cell cycle elongation or shortening was the main cause for abnormally low or high cell number, respectively. After excluding embryos with abnormal division behaviors, the developmental potential, implantation rate and live birth rate of day 3 embryos increased with cell number.
authors.affiliation: Institute of Reproductive and Stem Cell Engineering, college of basic medicine, Central South University, Changsha, China.|Key Laboratory of Reproductive and Stem Cell Engineering, Ministry of Health, Changsha, China.
authors.forename: Xiangyi
authors.initials: X
authors.lastname: Kong
authors.affiliation: Institute of Reproductive and Stem Cell Engineering, college of basic medicine, Central South University, Changsha, China.|Key Laboratory of Reproductive and Stem Cell Engineering, Ministry of Health, Changsha, China.
authors.forename: Shuting
authors.initials: S
authors.lastname: Yang
authors.affiliation: Institute of Reproductive and Stem Cell Engineering, college of basic medicine, Central South University, Changsha, China.|Key Laboratory of Reproductive and Stem Cell Engineering, Ministry of Health, Changsha, China.|Reproductive and Genetic Hospital of CITIC-Xiangya, Changsha, China.
authors.forename: Fei
authors.initials: F
authors.lastname: Gong
authors.affiliation: Institute of Reproductive and Stem Cell Engineering, college of basic medicine, Central South University, Changsha, China.|Key Laboratory of Reproductive and Stem Cell Engineering, Ministry of Health, Changsha, China.|Reproductive and Genetic Hospital of CITIC-Xiangya, Changsha, China.
authors.forename: Changfu
authors.initials: C
authors.lastname: Lu
authors.affiliation: Institute of Reproductive and Stem Cell Engineering, college of basic medicine, Central South University, Changsha, China.|Key Laboratory of Reproductive and Stem Cell Engineering, Ministry of Health, Changsha, China.|Reproductive and Genetic Hospital of CITIC-Xiangya, Changsha, China.
authors.forename: Shuoping
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Institute of Reproductive and Stem Cell Engineering, college of basic medicine, Central South University, Changsha, China.|Key Laboratory of Reproductive and Stem Cell Engineering, Ministry of Health, Changsha, China.|Reproductive and Genetic Hospital of CITIC-Xiangya, Changsha, China.|National Engineering and Research Center of Human Stem Cells, Changsha, China.
authors.forename: Guangxiu
authors.initials: G
authors.lastname: Lu
authors.affiliation: Institute of Reproductive and Stem Cell Engineering, college of basic medicine, Central South University, Changsha, China.|Key Laboratory of Reproductive and Stem Cell Engineering, Ministry of Health, Changsha, China.|Reproductive and Genetic Hospital of CITIC-Xiangya, Changsha, China.|National Engineering and Research Center of Human Stem Cells, Changsha, China.
authors.forename: Ge
authors.initials: G
authors.lastname: Lin
mesh_terms: D000328:Adult; D001755:Blastocyst / Q000166:cytology*; D002452:Cell Count; D002455:Cell Division; D046149:Embryo Culture Techniques / Q000379:methods*; D010064:Embryo Implantation; D047108:Embryonic Development; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D050498:Live Birth; D008297:Male; D011247:Pregnancy; D018873:Pregnancy Rate; D012189:Retrospective Studies; D020554:Sperm Injections, Intracytoplasmic; D059008:Time-Lapse Imaging / Q000379:methods*