title: Severe stress following bereavement during pregnancy and risk of pregnancy loss: results from a population-based cohort study.
abstract: BACKGROUND
  Previous findings on the association between stress during pregnancy and pregnancy loss are inconsistent. We aimed to estimate this association using a large prospective cohort.
  
  
  METHODS
  This population-based study included all 1 303 660 clinically recognised pregnancies in Denmark between 1995 and 2008. We categorised women as exposed to severe stress if they lost a child, sibling or parent during pregnancy. Cox Proportional Hazards models were used to study the association between exposure and rate of fetal death, starting with the follow-up on the day of completion of week 4 of pregnancy. In an attempt to control for unknown potential confounders, we also designed a pregnancy-matched analysis in which each woman had her own baseline risk of pregnancy loss and controls therefore for genetic and time-stable environmental factors.
  
  
  RESULTS
  A total of 146 031 pregnancies ended in clinically recognised fetal loss (11.2%) and a total of 10 808 (0.8%) women were categorised as exposed. The overall risk of pregnancy loss was similar in the exposed and unexposed (aHR=1.05, 95% CI 0.95 to 1.15). Results from the pregnancy-matched analysis (performed in 423 women) showed stronger and significant associations (aHR=1.83, 95% CI 1.49 to 2.25). All the analyses indicated a stronger effect of bereavement when the mother lost a child or when the death was unexpected.
  
  
  CONCLUSIONS
  Our main results suggested no strong association between severe stress during pregnancy and risk of pregnancy loss. Results from the pregnancy-matched analyses considered information from a selected and small group of women for whom there may exist a stronger association between stress during pregnancy and pregnancy loss. The fact that an unexpected death or the loss of a child had a stronger effect in both analyses may indicate that severe stressful situations increase the risk of pregnancy loss.
authors.affiliation: Section for Epidemiology, Department of Public Health, Aarhus University, Aarhus, Denmark.
authors.forename: Oleguer
authors.identifier: http://orcid.org/0000-0002-6470-7465
authors.initials: O
authors.lastname: Plana-Ripoll
authors.affiliation: Section for Biostatistics, Department of Public Health, Aarhus University, Aarhus, Denmark.
authors.forename: Erik
authors.initials: E
authors.lastname: Parner
authors.affiliation: Section for Epidemiology, Department of Public Health, Aarhus University, Aarhus, Denmark Department of Epidemiology, UCLA School of Public Health, Los Angeles, California, USA.
authors.forename: Jørn
authors.initials: J
authors.lastname: Olsen
authors.affiliation: Section for Epidemiology, Department of Public Health, Aarhus University, Aarhus, Denmark.
authors.forename: Jiong
authors.initials: J
authors.lastname: Li
mesh_terms: D000029:Abortion, Legal / Q000523:psychology*; D000022:Abortion, Spontaneous / Q000453:epidemiology / Q000523:psychology*; D000328:Adult; D001601:Bereavement; D015331:Cohort Studies; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D011247:Pregnancy; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012042:Registries; D013315:Stress, Psychological / Q000150:complications*; D055815:Young Adult
keywords: PREGNANCY; PSYCHOLOGICAL STRESS; REPRODUCTION