title: Maternal bereavement and the risk of preterm delivery: the importance of gestational age and of the precursor of preterm birth.
abstract: BACKGROUND
  Maternal stress during pregnancy may increase the risk of preterm delivery (PD), but the associations between stress and subtypes of PD are not clear. We investigated maternal loss of a close relative and risks of very and moderately PD (<32 and 32-36 weeks, respectively) and spontaneous and medically indicated PD.
  
  
  METHODS
  We studied 4 940 764 live singleton births in Denmark (1978-2008) and Sweden (1973-2006). We retrieved information on death of women's family members (children, partner, siblings, parents), birth outcomes and maternal characteristics from nationwide registries.
  
  
  RESULTS
  Overall, the death of a close family member the year before pregnancy or in the first 36 weeks of pregnancy was associated with a 7% increased risk of PD [95% confidence interval (CI) 1.04-1.10]. The highest hazard ratios (HR) for PD were found for death of an older child [HR (95% CI) 1.20 (1.10-1.31)] and for death of a partner [HR (95% CI) 1.31 (1.03-1.66)]. These losses were associated with higher risks of very preterm [HR (95% CI) 1.61 (1.29-2.01) and 2.07 (1.15-3.74), respectively] than of moderately preterm [HR (95% CI) 1.14 (1.03-1.26) and 1.22 (0.94-1.58), respectively] delivery. There were no substantial differences in the association between death of a child or partner and the risk of spontaneous v. medically indicated PD.
  
  
  CONCLUSIONS
  Death of a close family member the year before or during pregnancy was associated with an increased risk of PD, especially very PD. Possible mechanisms include both spontaneous and medically indicated preterm birth.
authors.affiliation: Clinical Epidemiology Unit, Department of Medicine,Karolinska University Hospital and Karolinska Institute,Stockholm,Sweden.
authors.forename: K D
authors.initials: KD
authors.lastname: László
authors.affiliation: Section for Epidemiology,Department of Public Health,Aarhus University,Aarhus,Denmark.
authors.forename: J
authors.initials: J
authors.lastname: Li
authors.affiliation: Section for Epidemiology,Department of Public Health,Aarhus University,Aarhus,Denmark.
authors.forename: J
authors.initials: J
authors.lastname: Olsen
authors.affiliation: Research Unit for General Practice,Department of Public Health,Aarhus University,Aarhus,Denmark.
authors.forename: M
authors.initials: M
authors.lastname: Vestergaard
authors.affiliation: Research Unit for General Practice,Department of Public Health,Aarhus University,Aarhus,Denmark.
authors.forename: C
authors.initials: C
authors.lastname: Obel
authors.affiliation: Clinical Epidemiology Unit, Department of Medicine,Karolinska University Hospital and Karolinska Institute,Stockholm,Sweden.
authors.forename: S
authors.initials: S
authors.lastname: Cnattingius
mesh_terms: D000328:Adult; D001601:Bereavement; D015331:Cohort Studies; D003718:Denmark; D005190:Family; D005260:Female; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007752:Obstetric Labor, Premature / Q000453:epidemiology*; D011247:Pregnancy; D011248:Pregnancy Complications / Q000523:psychology*; D016016:Proportional Hazards Models; D012042:Registries; D012307:Risk Factors; D013315:Stress, Psychological / Q000523:psychology*; D013548:Sweden; D055815:Young Adult
keywords: Bereavement; medically indicated preterm delivery; moderately preterm delivery; preterm delivery; spontaneous preterm delivery; stress; very preterm delivery