title: Validity of self-reported time to pregnancy.
abstract: BACKGROUND
  The reliability of retrospective time to pregnancy (TTP) has been established, but its validity has been assessed in only 1 study, which had a short follow-up.
  
  
  METHODS
  Ninety-nine women enrolled a decade earlier in a prospective TTP study were queried by means of mailed questionnaires about the duration of time they had required to become pregnant. Their responses were compared with their earlier data from daily diaries (gold standard).
  
  
  RESULTS
  One-third of women could not recall their earlier TTP either in menstrual cycles or calendar months. Only 17%-19% of women recalled their TTP exactly. Agreement increased to 41%-51%, 65%-72%, and 72%-77% when defined as +/-1, +/-2, and +/-3 months, respectively. Women with longer observed TTPs or previous pregnancies were more likely to under-report their TTP.
  
  
  CONCLUSIONS
  The findings raise questions about the commonly assumed validity of self-reported TTP. Recalled TTP may introduce error when estimating fecundability or classifying couples' fecundity status.
authors.affiliation: Division of Epidemiology, Statistics and Prevention Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Rockville, MD 20852, USA.
authors.forename: Maureen A
authors.initials: MA
authors.lastname: Cooney
authors.forename: Germaine M
authors.initials: GM
authors.lastname: Buck Louis
authors.forename: Rajeshwari
authors.initials: R
authors.lastname: Sundaram
authors.forename: Bridget M
authors.initials: BM
authors.lastname: McGuiness
authors.forename: Courtney D
authors.initials: CD
authors.lastname: Lynch
mesh_terms: D000328:Adult; D005260:Female; D005298:Fertility; D006801:Humans; D007407:Interviews as Topic; D016014:Linear Models; D011939:Mental Recall; D009518:New York; D011247:Pregnancy; D012189:Retrospective Studies; D011795:Surveys and Questionnaires; D013997:Time Factors; D055815:Young Adult