title: Failed fertilization: is it predictable?
abstract: OBJECTIVE
  The purpose of this review is to critically examine the ability of screening tests to predict fertilization failure.
  
  
  RESULTS
  Failed fertilization occurs in 5-10% of in-vitro fertilization cycles and 2-3% of intracytoplasmic sperm injection cycles. Failed fertilization may result from impaired spermatozoa, oocyte deficiencies or defects in the in-vitro sperm/oocyte medium. In the in-vitro fertilization setting most cases are caused by male factor deficiencies, whereas failure of oocyte activation is the most common cause of failed fertilization after intracytoplasmic sperm injection. Although the standard semen analysis has limited ability to predict fertilization failure, strict sperm morphology criteria, sperm-zona binding ratios and zona pellucida induced acrosome reaction tests provide increased capacity to avoid this outcome. The quality of the semen sample on the day of oocyte retrieval and fertilization performance in previous in-vitro fertilization cycles may also guide the appropriate use of intracytoplasmic sperm injection. However, the routine use of the latter technique in cases of non-male factor infertility is contraindicated.
  
  
  CONCLUSIONS
  The ever improving techniques highlighted in this analysis offer improved ability to predict failed fertilization.
authors.affiliation: Department of Obstetrics and Gynecology, Yale University, New Haven, Connecticut 06520-8063, USA.
authors.forename: Neal G
authors.initials: NG
authors.lastname: Mahutte
authors.forename: Aydin
authors.initials: A
authors.lastname: Arici
mesh_terms: D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D008297:Male; D011247:Pregnancy; D018873:Pregnancy Rate; D020554:Sperm Injections, Intracytoplasmic; D013084:Sperm-Ovum Interactions; D013094:Spermatozoa / Q000502:physiology; D017211:Treatment Failure; D015044:Zona Pellucida / Q000502:physiology