• J M Morris, C S Algert, and C L Roberts.
• Kolling Institute for Medical Research, University of Sydney, Sydney, NSW, Australia. jmorris@med.usyd.edu.au
• J. Thromb. Haemost. 2010 May 1; 8 (5): 998-1003.

Summary BackgroundPregnancy and the postpartum period are times of hypercoagulability, increasing the risk of pulmonary embolism. Better quantification of risk factors can help target women who are most likely to benefit from postpartum thromboprophylaxis with heparin.ObjectivesTo determine the incidence rate and timing of postpartum pulmonary embolism, and assess perinatal risk factors predictive of the event.Patients/MethodsAntenatal, delivery and postpartum admission records of a cohort of 510 889 pregnancies were analysed. Pulmonary embolism was identified from ICD-10 codes at delivery, transfer or upon readmission at any time in the postpartum period.ResultsPulmonary embolism occurred in 375 women and was most common postpartum. The rate of postpartum pulmonary embolism without an antecedent thrombotic event was 0.45 per 1000 births. By the end of 4 weeks postpartum, the weekly rate approached the background rate of pulmonary embolism in the population. Although the Caesarean section rate rose significantly throughout the study period, and pulmonary embolism was more common following abdominal birth, the rate of pulmonary embolism following Caesarean birth fell. Regression modelling demonstrated that stillbirth (adjusted odds ratio [aOR] =5.97), lupus (aOR = 8.83) and transfusion of a coagulation product (aOR = 8.84) were most strongly associated with pulmonary embolism postpartum.ConclusionsPulmonary embolism most commonly occurs up to 4 weeks postpartum and following abdominal birth. Despite this the absolute event rate is low and a broadly inclusive risk factor approach to the use of pharmacological thromboprophylaxis will require many women to be exposed to heparin to prevent an embolic event.

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