title: Incidence of pulmonary and venous thromboembolism in pregnancies after in vitro fertilisation: cross sectional study.
abstract: OBJECTIVE
  To estimate the risk of pulmonary embolism and venous thromboembolism in pregnant women after in vitro fertilisation.
  
  
  METHODS
  Cross sectional study.
  
  
  METHODS
  Sweden.
  
  
  METHODS
  23,498 women who had given birth after in vitro fertilisation between 1990 and 2008 and 116,960 individually matched women with natural pregnancies.
  
  
  METHODS
  Risk of pulmonary embolism and venous thromboembolism (identified by linkage to the Swedish national patient register) during the whole pregnancy and by trimester.
  
  
  RESULTS
  Venous thromboembolism occurred in 4.2/1000 women (n=99) after in vitro fertilisation compared with 2.5/1000 (n=291) in women with natural pregnancies (hazard ratio 1.77, 95% confidence interval 1.41 to 2.23). The risk of venous thromboembolism was increased during the whole pregnancy (P<0.001) and differed between the trimesters (P=0.002). The risk was particularly increased during the first trimester, at 1.5/1000 after in vitro fertilisation versus 0.3/1000 (hazard ratio 4.22, 2.46 to 7.26). The proportion of women experiencing pulmonary embolism during the first trimester was 3.0/10,000 after in vitro fertilisation versus 0.4/10,000 (hazard ratio 6.97, 2.21 to 21.96).
  
  
  CONCLUSIONS
  In vitro fertilisation is associated with an increased risk of pulmonary embolism and venous thromboembolism during the first trimester. The risk of pulmonary embolism is low in absolute terms but because the condition is a leading cause of maternal mortality and clinical suspicion is critical for diagnosis, an awareness of this risk is important.
  
  
  BACKGROUND
  ClinicalTrials.gov NCT01524393.
authors: Division of Cardiovascular Medicine, Department of Clinical Sciences, Danderyd Hospital, Karolinska Institutet, SE 182 88 Stockholm, Sweden. peter.henriksson@ki.se
authors: Peter
authors: P
authors: Henriksson
authors: Eli
authors: E
authors: Westerlund
authors: Håkan
authors: H
authors: Wallén
authors: Lena
authors: L
authors: Brandt
authors: Outi
authors: O
authors: Hovatta
authors: Anders
authors: A
authors: Ekbom
mesh_terms: D000328:Adult; D003430:Cross-Sectional Studies; D005260:Female; D005307:Fertilization in Vitro / Q000009:adverse effects*; D006801:Humans; D008875:Middle Aged; D015999:Multivariate Analysis; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D016016:Proportional Hazards Models; D011655:Pulmonary Embolism / Q000453:epidemiology / Q000209:etiology*; D012042:Registries; D012307:Risk Factors; D013548:Sweden / Q000453:epidemiology; D054556:Venous Thromboembolism / Q000453:epidemiology / Q000209:etiology*