title: Techniques for cryopreservation of individual or small numbers of human spermatozoa: a systematic review.
abstract: BACKGROUND
  Despite interest in cryopreservation of individual or small number of human spermatozoa, to date, little data is available as regards its effectiveness. We systematically reviewed the outcome after cryopreservation of individual or small numbers of human spermatozoa in patients with severe male factor of infertility.
  
  
  METHODS
  We searched the MEDLINE, EMBASE, Cochrane Systematic Reviews, CENTRAL, Web of Science, Scopus databases for relevant studies up to June of 2008. The search used terms referring to cryopreservation of small amount of sperm. Included studies were limited to human studies with no language restrictions.
  
  
  RESULTS
  We identified 30 reports including 9 carriers used for cryopreservation of small quantities/numbers of human spermatozoa (7 non-biological and 2 biological carriers). A wide variety of cryopreservation vehicles were reported. The recovery rate of spermatozoa cryopreserved in a known small number varied widely from 59 to 100%. Fertilization rates were in the range of 18-67%. Frozen-thawed spermatozoa, using this method, were subsequently used for intracytoplasmic sperm injection in only five studies, with few pregnancies reported so far. To date, there remains no consensus as to the ideal carrier for cryopreservation of small number of spermatozoa for clinical purposes.
  
  
  CONCLUSIONS
  Cryopreservation of individual or small numbers of human spermatozoa may replace the need for repeated surgical sperm retrieval. A controlled multicenter trial with sufficient follow-up would provide valid evidence of the potential benefit of this approach.
authors.affiliation: Department of Obstetrics and Gynecology, Cleveland Clinic Fertility Centre, Cleveland Clinic Foundation, OH 44122, USA.
authors.forename: Faten
authors.initials: F
authors.lastname: AbdelHafez
authors.forename: Mohamed
authors.initials: M
authors.lastname: Bedaiwy
authors.forename: Sherif A
authors.initials: SA
authors.lastname: El-Nashar
authors.forename: Edmund
authors.initials: E
authors.lastname: Sabanegh
authors.forename: Nina
authors.initials: N
authors.lastname: Desai
mesh_terms: D015331:Cohort Studies; D015925:Cryopreservation / Q000379:methods*; D003451:Cryoprotective Agents; D005260:Female; D006801:Humans; D008297:Male; D011247:Pregnancy; D011256:Pregnancy Outcome; D027724:Reproductive Techniques, Assisted; D053625:Sperm Retrieval; D013094:Spermatozoa
chemical_list: D003451:Cryoprotective Agents