title: Effect of preovulatory progesterone elevation and duration of progesterone elevation on the pregnancy rate of frozen-thawed embryo transfer in natural cycles.
abstract: OBJECTIVE
  To assess the incidence of P elevation (PE) in natural cycles and evaluate its effect on frozen-thawed embryo transfer cycles performed in natural cycles (FET-NC).
  
  
  METHODS
  Retrospective analysis.
  
  
  METHODS
  A tertiary assisted reproductive unit.
  
  
  METHODS
  Subfertile woman who did not conceive in their stimulated IVF cycle and underwent the first FET-NC cycle.
  
  
  METHODS
  Achieved serum samples were assayed for P concentrations from the day of LH surge up to 3 days before the surge. The cutoff level of PE was defined as 5 nmol/L.
  
  
  METHODS
  Clinical and ongoing pregnancy rates.
  
  
  RESULTS
  The incidence of PE in natural cycles was 173 of 610 (28.4%). There were no significant differences in both clinical and ongoing pregnancy rates (39.0% vs. 37.3% and 32.5% vs. 31.7%) between those with vs. without PE on the day of LH surge. If PE lasted for 2 days or more, there was a significant reduction in the clinical pregnancy rate (39.4% vs. 20.7%). Using multivariate logistic regression, women's age, PE for 2 days or more, and the number of top-quality embryos were the significant factors for clinical pregnancy rates in FET-NC.
  
  
  CONCLUSIONS
  The incidence of PE in FET-NC was similar to that in stimulated cycles. Progesterone elevation for 2 days or more before the LH surge impaired the clinical pregnancy rate of FET-NC, whereas PE on the day of LH surge only did not have such an adverse effect.
authors.affiliation: Department of Obstetrics and Gynecology, University of Hong Kong, Hong Kong, People's Republic of China. Electronic address: v200lee@hku.hk.
authors.forename: Vivian Chi Yan
authors.initials: VC
authors.lastname: Lee
authors.affiliation: Department of Obstetrics and Gynecology, University of Hong Kong, Hong Kong, People's Republic of China.
authors.forename: Raymond Hang Wun
authors.initials: RH
authors.lastname: Li
authors.affiliation: Department of Obstetrics and Gynecology, University of Hong Kong, Hong Kong, People's Republic of China.
authors.forename: Joyce
authors.initials: J
authors.lastname: Chai
authors.affiliation: Department of Obstetrics and Gynecology, University of Hong Kong, Hong Kong, People's Republic of China.
authors.forename: Tracy Wing Yee
authors.initials: TW
authors.lastname: Yeung
authors.affiliation: Department of Obstetrics and Gynecology, University of Hong Kong, Hong Kong, People's Republic of China.
authors.forename: William Shu Biu
authors.initials: WS
authors.lastname: Yeung
authors.affiliation: Department of Obstetrics and Gynecology, University of Hong Kong, Hong Kong, People's Republic of China.
authors.forename: Pak Chung
authors.initials: PC
authors.lastname: Ho
authors.affiliation: Department of Obstetrics and Gynecology, University of Hong Kong, Hong Kong, People's Republic of China.
authors.forename: Ernest Hung Yu
authors.initials: EH
authors.lastname: Ng
mesh_terms: D000328:Adult; D015925:Cryopreservation / Q000639:trends*; D004624:Embryo Transfer / Q000639:trends*; D005260:Female; D005498:Follicular Phase / Q000097:blood / Q000502:physiology*; D006801:Humans; D007247:Infertility, Female / Q000097:blood* / Q000628:therapy*; D008875:Middle Aged; D011247:Pregnancy; D018873:Pregnancy Rate / Q000639:trends*; D011374:Progesterone / Q000096:biosynthesis / Q000097:blood / Q000502:physiology*; D012189:Retrospective Studies; D013997:Time Factors; D015854:Up-Regulation / Q000502:physiology; D055815:Young Adult
chemical_list: D011374:Progesterone
keywords: Frozen–thawed embryo transfer; natural cycle; progesterone elevation