title: Triggers of spontaneous preterm delivery--why today?
abstract: BACKGROUND
  Our goal is to study the triggers of spontaneous preterm delivery using a case-crossover design.
  
  
  METHODS
  In a pilot study, we enrolled 50 women with spontaneous preterm labour (PTL) and 50 with preterm premature rupture of membranes (PPROM) between 2011 and 2012. To assess non-transient risk factors, we also enrolled a control group of 158 pregnant women at their regular prenatal care visits matched to cases by gestational age and calendar time. The index time was defined as the onset of PTL/PPROM (for cases) or interview (for controls). Detailed data were collected through structured interviews regarding factors of interest during the 72 h that preceded the index time. Within case subjects, we compared the frequency of transient factors from 0 to 24 h before index time with that from 48 to 72 h before index time, and estimated matched odds ratios (OR) and 95% confidence intervals (CI).
  
  
  RESULTS
  Previously hypothesised chronic risk factors for spontaneous preterm delivery, including mood disorders and stressful events, were more common among cases than among controls. Within cases, skipped meals [OR 4.3, 95% CI 1.2, 15.2], disturbed sleep [OR 4.5, 95% CI 1.5, 13.3], sexual activity [OR 6.0, 95% CI 0.7, 69.8], and intake of spicy foods [OR 7.0, 95% CI 1.6, 30.8] were associated with an increased risk for PTL/PPROM within the subsequent 24 h. For physical exertion and other potential risk factors evaluated, the OR was close to the null.
  
  
  CONCLUSIONS
  Skipping meals and disturbed sleep may be associated with imminent PTL/PPROM; sexual activity and spicy food may trigger PTL/PPROM in susceptible women. Larger case-crossover studies will be able to evaluate the impact of modifiable risk factors and acute predictors of PTL/PPROM, and might help guide obstetrical management.
authors.affiliation: Department of Epidemiology, Harvard School of Public Health, Boston, MA.
authors.forename: Sonia
authors.initials: S
authors.lastname: Hernández-Díaz
authors.forename: Caroline E
authors.initials: CE
authors.lastname: Boeke
authors.forename: Anna Thornton
authors.initials: AT
authors.lastname: Romans
authors.forename: Brett
authors.initials: B
authors.lastname: Young
authors.forename: Andrea V
authors.initials: AV
authors.lastname: Margulis
authors.forename: Thomas F
authors.initials: TF
authors.lastname: McElrath
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Ecker
authors.forename: Brian T
authors.initials: BT
authors.lastname: Bateman
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D003075:Coitus; D018592:Cross-Over Studies; D005247:Feeding Behavior; D005260:Female; D005322:Premature Rupture of Fetal Membranes / Q000453:epidemiology / Q000209:etiology* / Q000517:prevention & control; D005865:Gestational Age; D006801:Humans; D007752:Obstetric Labor, Premature / Q000453:epidemiology / Q000209:etiology* / Q000517:prevention & control; D010865:Pilot Projects; D011237:Predictive Value of Tests; D011247:Pregnancy; D018566:Pregnancy, High-Risk; D011295:Prenatal Care / Q000379:methods*; D012307:Risk Factors; D012892:Sleep Deprivation; D011795:Surveys and Questionnaires
keywords: case-crossover design; preterm labour; risk factors; spontaneous rupture of membranes