title: Herniated blastomere following chemically assisted hatching may result in monozygotic twins.
abstract: OBJECTIVE
  To explore a possible mechanism of the increasing incidence of monozygotic twins following assisted hatching of human embryos.
  
  
  METHODS
  Case report.
  
  
  METHODS
  Clinical research center in a medical school teaching hospital.
  
  
  METHODS
  A 37-year-old infertile woman with repeated IVF failures.
  
  
  METHODS
  Assisted hatching of the day 3 embryos using acidic Tyrode's solution.
  
  
  METHODS
  The morphology of the zona-drilled embryos and the pregnancy outcome.
  
  
  RESULTS
  After assisted hatching, a herniated blastomere through an oversized opening in the zona pellucida was found in one embryo. The transfer of two zona-drilled embryos resulted in a triplet pregnancy.
  
  
  CONCLUSIONS
  Large openings in the zona pellucida following chemically assisted hatching may cause premature hatching of the blastomeres and may be implicated in the occurrence of monozygotic twins.
authors.affiliation: Center for Reproductive Medicine, Department of Obstetrics and Gynecology, Taipei Medical College Hospital, #252, Wu Hsing Street, Taipei 110, Taiwan.
authors.forename: T C
authors.initials: TC
authors.lastname: Sheen
authors.forename: S R
authors.initials: SR
authors.lastname: Chen
authors.forename: H K
authors.initials: HK
authors.lastname: Au
authors.forename: Y Y
authors.initials: YY
authors.lastname: Chien
authors.forename: K Y
authors.initials: KY
authors.lastname: Wu
authors.forename: C R
authors.initials: CR
authors.lastname: Tzeng
mesh_terms: D000328:Adult; D001757:Blastomeres / Q000502:physiology / Q000648:ultrastructure*; D006063:Chorionic Gonadotropin / Q000008:administration & dosage; D046508:Culture Techniques; D010064:Embryo Implantation; D004624:Embryo Transfer; D005260:Female; D005640:Follicle Stimulating Hormone / Q000008:administration & dosage; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008596:Menotropins / Q000008:administration & dosage; D011247:Pregnancy; D011256:Pregnancy Outcome; D020554:Sperm Injections, Intracytoplasmic; D014310:Triplets; D014430:Twins, Monozygotic; D015044:Zona Pellucida / Q000648:ultrastructure
chemical_list: D006063:Chorionic Gonadotropin; D008596:Menotropins; D005640:Follicle Stimulating Hormone