title: A comparison of headfirst and tailfirst microinjection of sperm at intracytoplasmic sperm injection.
abstract: OBJECTIVE
  To investigate whether the direction of sperm loading and exit from the injection pipette during intracytoplasmic sperm injection (ICSI) had any bearing on ability to cause fertilization or affect subsequent embryonic development.
  
  
  METHODS
  Prospective randomized trial.
  
  
  METHODS
  Hospital-based IVF center.
  
  
  METHODS
  Twenty-five couples participating in an intracytoplasmic sperm injection (ICSI) program.
  
  
  METHODS
  Sperm microinjection was randomly divided into either headfirst injection or tailfirst injection.
  
  
  METHODS
  Fertilization, embryo quality, and implantation rates.
  
  
  RESULTS
  There were no significant differences in the fertilization rates or the proportion of good-quality embryos, according to the direction of sperm injection. Of the embryos selected for transfer, 41.3% originated from headfirst sperm injection, and 58.7%, from tailfirst sperm injection. After transfer of either two or three embryos into 24 patients, 11 embryos implanted, with an equal probability that these embryos originated from either headfirst or tailfirst sperm injection. However, one dizygotic twin pregnancy was traced to the transfer of two embryos; one resulted from headfirst sperm injection, and one from tailfirst sperm injection.
  
  
  CONCLUSIONS
  The direction of sperm microinjection at ICSI appears to have no effect on fertilization or subsequent development. The preliminary findings of this study have some interesting practical implications for the procedure of ICSI.
authors.affiliation: School of Biosciences, University of Nottingham, Sutton Bonington, Leicestershire, United Kingdom. theeggman68@hotmail.com
authors.forename: Bryan J
authors.initials: BJ
authors.lastname: Woodward
authors.forename: Keith H S
authors.initials: KH
authors.lastname: Campbell
authors.forename: Samuel S
authors.initials: SS
authors.lastname: Ramsewak
mesh_terms: D010064:Embryo Implantation; D004624:Embryo Transfer; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D007248:Infertility, Male / Q000628:therapy*; D008297:Male; D008845:Microinjections; D011247:Pregnancy; D018873:Pregnancy Rate; D011446:Prospective Studies; D020554:Sperm Injections, Intracytoplasmic / Q000379:methods*; D016896:Treatment Outcome