title: Determinants of unexplained antepartum fetal deaths.
abstract: OBJECTIVE
  To assess fetal, maternal, and pregnancy-related determinants of unexplained antepartum fetal death.
  
  
  METHODS
  We conducted a hospital-based cohort study of 84,294 births weighing 500 g or more from 1961-1974 and 1978-1996. Unexplained fetal deaths were defined as fetal deaths occurring before labor without evidence of significant fetal, maternal, or placental pathology.
  
  
  RESULTS
  One hundred ninety-six unexplained antepartum fetal deaths accounted for 27.2% of 721 total fetal deaths. Two thirds of the unexplained fetal deaths occurred after 35 weeks' gestation. The following factors were independently associated with unexplained fetal death: maternal prepregnancy weight greater than 68 kg (adjusted odds ratio [OR] 2.9; 95% confidence interval [CI] 1.85, 4.68), birth weight ratio (defined as ratio of birth weight to mean weight for gestational age) between 0.75 and 0.85 (OR 2.77; 95% CI 1.48, 5.18) or over 1.15 (OR 2.36; 95% CI 1.26, 4.44), fewer than four antenatal visits in women whose fetuses died at 37 weeks or later (OR 2.21; 95% CI 1.08, 4.52), primiparity (OR 1.74; 95% CI 1.26, 2.40), parity of three or more (OR 2.01; 95% CI 1.26, 3.20), low socioeconomic status (OR 1.59; 95% CI 1.14, 2.22), cord loops (OR 1.75; 95% CI 1.04, 2.97) and, for the 1978-1996 period only, maternal age 40 years or more (OR 3.69; 95% CI 1.28, 10.58). Trimester of first antenatal visit, low maternal weight, postdate pregnancy, fetal-to-placental weight ratio, fetal sex, previous fetal death, previous abortion, cigarette smoking, and alcohol use were not significantly associated with unexplained fetal death.
  
  
  CONCLUSIONS
  In this study, we identified several factors associated with an increased risk of unexplained fetal death.
authors.affiliation: Department of Obstetrics and Gynecology, Royal Victoria Hospital, McGill University, Montreal, Quebec, Canada.
authors.forename: D Y
authors.initials: DY
authors.lastname: Huang
authors.forename: R H
authors.initials: RH
authors.lastname: Usher
authors.forename: M S
authors.initials: MS
authors.lastname: Kramer
authors.forename: H
authors.initials: H
authors.lastname: Yang
authors.forename: L
authors.initials: L
authors.lastname: Morin
authors.forename: R C
authors.initials: RC
authors.lastname: Fretts
mesh_terms: D000328:Adult; D015331:Cohort Studies; D016001:Confidence Intervals; D005260:Female; D005313:Fetal Death / Q000453:epidemiology* / Q000209:etiology*; D006801:Humans; D007231:Infant, Newborn; D009765:Obesity / Q000150:complications; D016017:Odds Ratio; D010298:Parity; D011247:Pregnancy; D011295:Prenatal Care; D011792:Quebec / Q000453:epidemiology; D012307:Risk Factors; D012923:Social Class