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Comparative Study
. 2013 Jan 15:346:e8632.
doi: 10.1136/bmj.e8632.

Incidence of pulmonary and venous thromboembolism in pregnancies after in vitro fertilisation: cross sectional study

Peter Henriksson  1 , Eli Westerlund, Håkan Wallén, Lena Brandt, Outi Hovatta, Anders Ekbom
Affiliations
Comparative Study

Incidence of pulmonary and venous thromboembolism in pregnancies after in vitro fertilisation: cross sectional study

Peter Henriksson et al. BMJ. .

Abstract

Objective: To estimate the risk of pulmonary embolism and venous thromboembolism in pregnant women after in vitro fertilisation.

Design: Cross sectional study.

Setting: Sweden.

Participants: 23,498 women who had given birth after in vitro fertilisation between 1990 and 2008 and 116,960 individually matched women with natural pregnancies.

Main outcome measures: 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.

Trial registration: ClinicalTrials.gov NCT01524393.

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Conflict of interest statement

Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; and no other relationships or activities that could appear to have influenced the submitted work.

Figures

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Fig 1 Proportional hazard regression of venous thromboembolism in pregnant women after in vitro fertilisation (n=23 498) and in women with natural pregnancies (n=11 960) matched on age and calendar period of delivery
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Fig 2 Proportional hazard regression of pulmonary embolism in pregnant women after in vitro fertilisation (n=23 498) and in women with natural pregnancies (n=11 960) matched on age and calendar period of delivery
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Fig 3 Time trends of incidence of registered venous thromboembolic (VTE) diagnoses per 1000 pregnant women after in vitro fertilisation and women with natural pregnancies matched on age and calendar period of delivery in Swedish national patient register, National Board of Health and Welfare
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Fig 4 Proportional hazard regression of venous thromboembolism in three strata for body mass index (<25, 25-29.9, and ≥30) in pregnant women after in vitro fertilisation (n=23 498) and in women with natural pregnancies (n=116 960) matched on age and calendar period of delivery
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