title: Cumulative pregnancy rates after a maximum of nine cycles of modified natural cycle IVF and analysis of patient drop-out: a cohort study.
abstract: BACKGROUND
  In modified natural cycle IVF (MNV-IVF), treatment is aimed at using the one follicle that spontaneously develops to dominance, using a GnRH antagonist together with gonadotrophins in the late follicular phase only.
  
  
  METHODS
  In this single-centre cohort study, nine cycles of MNV-IVF were offered to 268 patients. Cumulative pregnancy rates (CPRs) were calculated and drop-out was analysed. The present study is an extension of earlier studies in which three cycles of MNV-IVF were offered to the same patients.
  
  
  RESULTS
  A total of 256 patients completed 1048 cycles (4.1 per patient). Embryo transfer rate was 36.5% per started cycle. Ongoing pregnancy rate was 7.9% per started cycle and 20.7% per embryo transfer. Including treatment-independent pregnancies, the observed CPR after up to nine cycles was 44.4% (95% confidence interval 38.3-50.5) per patient. Pregnancy rates per started cycle did not decline in higher cycle numbers (overall 9.9%). Drop-out rates were high (overall 47.8%). We found that cancellation of oocyte retrieval, fertilization failure and failure to reach embryo transfer are repeating phenomena in subsequent cycles and furthermore that these events predispose for drop-out.
  
  
  CONCLUSIONS
  CPR after nine cycles of MNV-IVF in this study was 44.4%. Pregnancy rate per cycle did not decline in higher cycle numbers, possibly due to selective drop-out of poor prognosis patients. Due to the low-risk and patient-friendly nature of the MNC protocol, it seems a feasible treatment option for patients requiring IVF.
authors.affiliation: Section of Reproductive Medicine, Department of Obstetrics and Gynaecology, University Medical Center Groningen, Groningen, The Netherlands. pelinck@hotmail.com
authors.forename: M J
authors.initials: MJ
authors.lastname: Pelinck
authors.forename: N E A
authors.initials: NE
authors.lastname: Vogel
authors.forename: E G J M
authors.initials: EG
authors.lastname: Arts
authors.forename: A H M
authors.initials: AH
authors.lastname: Simons
authors.forename: M J
authors.initials: MJ
authors.lastname: Heineman
authors.forename: A
authors.initials: A
authors.lastname: Hoek
mesh_terms: D000328:Adult; D015331:Cohort Studies; D004624:Embryo Transfer; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods*; D006801:Humans; D007247:Infertility, Female / Q000628:therapy*; D009426:Netherlands; D010352:Patient Dropouts; D011247:Pregnancy; D018873:Pregnancy Rate