title: Rates of preterm birth following antenatal maternal exposure to severe life events: a population-based cohort study.
abstract: BACKGROUND
  Preterm birth and other pregnancy complications have been linked to maternal stress during pregnancy. We investigated the association between maternal exposure to severe life events and risk of preterm birth.
  
  
  METHODS
  Mothers of all singleton live births (n = 1.35 million births) in Denmark between 1 January 1979 and 31 December 2002 were linked to data on their children, parents, siblings and partners. We defined exposure as death or serious illness in close relatives in the first or second trimesters or in the 6 months before conception. Log-linear binomial regression was used to estimate the effect of exposure on preterm birth, very preterm birth and extremely preterm birth.
  
  
  RESULTS
  There were 58 626 (4.34%) preterm births (<37 weeks), 11 732 (0.87%) very preterm births and 3288 (0.24%) extremely preterm births in the study cohort. Severe life events in close relatives in the 6 months before conception increased the risk of preterm birth by 16% (relative risk, RR = 1.16, [95% CI: 1.08-1.23]). Severe life events in older children in the 6 months before conception increased the risk of preterm birth by 23% (RR = 1.23, [95% CI: 1.02-1.49]) and the risk of very preterm birth by 59% (RR = 1.59, [95% CI: 1.08-2.35]).
  
  
  CONCLUSIONS
  Our population-based cohort study suggests that maternal exposure to severe life events, particularly in the 6 months before pregnancy, may increase the risk of preterm and very preterm birth.
authors.affiliation: Centre for Women's Mental Health, University of Manchester, Manchester, UK. a.khashan@ucc.ie
authors.forename: A S
authors.initials: AS
authors.lastname: Khashan
authors.forename: R
authors.initials: R
authors.lastname: McNamee
authors.forename: K M
authors.initials: KM
authors.lastname: Abel
authors.forename: P B
authors.initials: PB
authors.lastname: Mortensen
authors.forename: L C
authors.initials: LC
authors.lastname: Kenny
authors.forename: M G
authors.initials: MG
authors.lastname: Pedersen
authors.forename: R T
authors.initials: RT
authors.lastname: Webb
authors.forename: P N
authors.initials: PN
authors.lastname: Baker
mesh_terms: D000328:Adult; D015331:Cohort Studies; D005190:Family; D005260:Female; D006801:Humans; D008016:Life Change Events; D011247:Pregnancy; D047928:Premature Birth / Q000453:epidemiology*; D012307:Risk Factors; D013997:Time Factors