title: Prospective evaluation of luteal phase length and natural fertility.
abstract: To evaluate the impact of a short luteal phase on fecundity.
  
  
  
  Prospective time-to-pregnancy cohort study.
  
  
  
  Not applicable.
  
  
  
  Women trying to conceive, ages 30-44 years, without known infertility.
  
  
  
  Daily diaries, ovulation prediction testing, standardized pregnancy testing.
  
  
  
  Subsequent cycle fecundity.
  
  
  
  Included in the analysis were 1,635 cycles from 284 women. A short luteal phase (≤11 days including the day of ovulation) occurred in 18% of observed cycles. Mean luteal phase length was 14 days. Significantly more women with a short luteal phase were smokers. After adjustment for age, women with a short luteal phase had 0.82 times the odds of pregnancy in the subsequent cycle immediately following the short luteal phase compared with women without a short luteal phase. Women with a short luteal length in the first observed cycle had significantly lower fertility after the first 6 months of pregnancy attempt, but at 12 months there was no significant difference in cumulative probability of pregnancy.
  
  
  
  Although an isolated cycle with a short luteal phase may negatively affect short-term fertility, incidence of infertility at 12 months was not significantly higher among these women.
  
  
  
  NCT01028365.
authors.affiliation: Department of Obstetrics and Gynecology, University of North Carolina, Chapel Hill, North Carolina. Electronic address: nmcraw@gmail.com.
authors.forename: Natalie M
authors.initials: NM
authors.lastname: Crawford
authors.affiliation: Department of Biostatistics, University of North Carolina, Chapel Hill, North Carolina.
authors.forename: David A
authors.initials: DA
authors.lastname: Pritchard
authors.affiliation: Department of Biostatistics, University of North Carolina, Chapel Hill, North Carolina.
authors.forename: Amy H
authors.initials: AH
authors.lastname: Herring
authors.affiliation: Department of Obstetrics and Gynecology, University of North Carolina, Chapel Hill, North Carolina.
authors.forename: Anne Z
authors.initials: AZ
authors.lastname: Steiner
mesh_terms: D000328:Adult; D005260:Female; D005298:Fertility; D006801:Humans; D053208:Kaplan-Meier Estimate; D008183:Luteal Phase / Q000502:physiology*; D016017:Odds Ratio; D010061:Ovulation Detection; D044384:Ovulation Prediction; D011247:Pregnancy; D011258:Pregnancy Tests; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012307:Risk Factors; D013997:Time Factors; D061685:Time-to-Pregnancy
keywords: Short luteal phase; fecundity; luteal phase deficiency; natural fertility