title: Natural cycle IVF: evaluation of 463 cycles and summary of the current literature.
abstract: OBJECTIVE
  Natural cycle (NC) IVF/ICSI has proven to be an alternative to conventional IVF/ICSI cycles.
  
  
  METHODS
  Within our retrospective, observational study (n = 159) infertile couples underwent (n = 463) cycles of NC-IVF/ICSI from May 2007 until December 2011. Oocyte pick-up was performed within a pure natural cycle excluding any hormonal stimulation except of hCG for ovulation induction. Oocytes were fertilized by IVF/ICSI and embryo transfer took place 2 or 3 days later. In addition, the current literature was analysed concerning pregnancy rates in NC-IVF/ICSI cycles.
  
  
  RESULTS
  Oocyte pick-up was performed in n = 463 NC and was successful in n = 342 cases (IVF n = 135, ICSI n = 207). 203 oocytes were fertilized (IVF n = 87, ICSI n = 116, FR 59.4 %) and lead to 192 embryo transfers. Finally, 25 pregnancies were reached (PR 13.0 % per transfer) resulting in four biochemical pregnancies, 7 (33.3 %) miscarriages, one pregnancy of unknown outcome and 13 live births. Within the current literature (n = 27 studies), PR in NC-IVF/ICSI cycles varied between 10.2 and 50 %.
  
  
  CONCLUSIONS
  Within our study, pregnancy rates in pure NC-IVF/ICSI remained below 15 %. Although this may be linked to unfavourable preconditions like patients' age >40 years, low ovarian reserve or long duration of infertility, further improvement is necessary to increase pregnancy rates.
authors.affiliation: Department of Gynecological Endocrinology and Fertility Disorders, Ruprecht-Karls University of Heidelberg, Voßstr. 9, 69115, Heidelberg, Germany, sabine.roesner@med.uni-heidelberg.de.
authors.forename: Sabine
authors.initials: S
authors.lastname: Roesner
authors.forename: Ulrike
authors.initials: U
authors.lastname: Pflaumer
authors.forename: Ariane
authors.initials: A
authors.lastname: Germeyer
authors.forename: Markus
authors.initials: M
authors.lastname: Montag
authors.forename: Thomas
authors.initials: T
authors.lastname: Strowitzki
authors.forename: Bettina
authors.initials: B
authors.lastname: Toth
mesh_terms: D000022:Abortion, Spontaneous; D000328:Adult; D006063:Chorionic Gonadotropin / Q000627:therapeutic use; D004624:Embryo Transfer; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods*; D006801:Humans; D050498:Live Birth; D008597:Menstrual Cycle; D008875:Middle Aged; D010062:Ovulation Induction; D011247:Pregnancy; D018873:Pregnancy Rate; D012102:Reproductive Control Agents / Q000627:therapeutic use; D012189:Retrospective Studies
chemical_list: D006063:Chorionic Gonadotropin; D012102:Reproductive Control Agents