Regular article
Maternal smoking, obesity, and risk of venous thromboembolism during pregnancy and the puerperium: A population-based nested case-control study

https://doi.org/10.1016/j.thromres.2006.12.003Get rights and content

Abstract

Background

Smoking and obesity are associated with adverse pregnancy outcomes. The aim of the present study was to examine the association between smoking, obesity (BMI > 30), and risk for venous thromboembolism (VTE) during pregnancy and the puerperium.

Materials and methods

In a population-based case-control study nested within a Danish cohort of 71,729 women, we identified 129 cases with VTE in pregnancy or the puerperium, and 258 pregnant non-VTE controls. We obtained data from medical records regarding current smoking status, BMI, and other covariates, and computed the odds ratios (OR) for VTE as a measure of relative risk.

Results

Smoking and obesity were associated with increased risk of VTE during pregnancy and the puerperium (adjusted OR 2.7 (95% CI: 1.5, 4.9) and 5.3 (95% CI: 2.1, 13.5), respectively). Obesity appeared to be associated with a higher risk of pulmonary embolism (adjusted OR: 14.9 (95% CI: 3.0, 74.8) than of deep venous thrombosis (adjusted OR: 4.4, 95% CI: 1.6, 11.9).

Conclusion

Smoking and obesity are risk factors for VTE in pregnancy and the puerperium.

Introduction

VTE is a rare but serious complication of pregnancy or the puerperium and pulmonary embolism (PE) is a common cause of maternal death in the Western world. Identification of possible risk factors and development of effective preventive strategies of pregnancy and puerperium related VTE events is therefore required. It is not clear to which extent findings on possible risk factors of VTE among men and non-pregnant women can be generalized to pregnant and puerperal women as pregnancy and puerperium in itself are associated with an increased risk VTE. So far the well-established risk factors for VTE during pregnancy and the puerperium only include a personal or family history of VTE, a non-O blood group, and hereditary or acquired hypercoagulable disorders [1], [2], [3], [7], [8], [9].

Smoking and obesity are associated with adverse pregnancy outcomes, including ectopic pregnancy, placental abruption, placenta previa, and preterm premature rupture of the membrane, pre-eclampsia, diabetes (pregestational and gestational), caesarean section and infections [1], [2], [3]. Both smoking and obesity have also been associated with an increased risk of VTE among men and non-pregnant women [4], [5], however, so far only few studies have examined the effect of smoking and obesity on the risk of VTE during pregnancy and puerperium [6], [7]. A large Swedish register study found a tobacco consumption-dependent increase in the risk of VTE among pregnant smokers [6], and a population-based case-control study from North America among women with a first lifetime VTE during pregnancy or postpartum found that smoking was an independent risk factor for VTE [7]. Data on obesity and VTE in relation to pregnancy are even fewer and further studies are clearly needed [7].

To clarify to which extent smoking and obesity are VTE risk factors in pregnancy and the puerperium, we conducted a population-based case-control study within a large cohort of pregnant and puerperal women in North Jutland County, Denmark.

Section snippets

Study design and population

We conducted this nested case-control study within a cohort of 71,729 women who had given birth to 126,783 children (including 102 stillbirths) in North Jutland County, Denmark (whose total population is about half a million residents) during the period from 1 January 1980 to 31 December 2001. The women and their births were all registered in the local Birth Registry which is part of a national birth surveillance program initiated in 1973. The Registry holds information about the birth, birth

Results

We identified 129 cases of VTE (112 cases of deep venous thrombosis and 17 cases of pulmonary embolism) and 258 controls (Table 1). Sixty-one VTE events were observed during pregnancy (47.3%) and 68 events during the postpartum period (52.7%). Smoking and obesity in an early stage of pregnancy were associated with VTE (adjusted OR 2.7, 95% CI: 1.5, 4.9, for smoking and 5.3, 95% CI: 2.1, 13.5, for obesity) (Table 2).

Smoking and obesity were associated with increased risk estimates both during

Discussion

We found that smoking and obesity in an early stage of pregnancy were associated with increased risk of VTE during in particular pregnancy and to a lesser extent puerperium.

Some research, primarily based on non-pregnancy related events, has suggested that smoking may be associated with an increased risk of VTE [10], [11]. However, only a few studies have looked at maternal smoking as a potential risk factors for VTE during pregnancy. In a population-based case-control study of 90

Acknowledgements

The study was supported by the Western Danish Research Forum for Health Sciences, and the Health Insurance Foundation “DANMARK” (F95-014).

References (15)

There are more references available in the full text version of this article.

Cited by (0)

View full text