Proteinuria and venous thromboembolism in pregnancy: a population-based cohort study

Abstract

Abstract Background Pregnancy-associated venous thromboembolism (VTE) is associated with high morbidity and mortality. Identification of risk factors of VTE may lead to improved maternal and foetal outcomes. Proteinuria confers a pro-thrombotic state, however, its association with VTE in pregnancy remains unknown. We set out to assess the association of proteinuria and VTE during pregnancy. Methods We conducted a population-based, retrospective cohort study of all pregnant women (≥16\u2009years of age) with a proteinuria measure within 20\u2009weeks of conception (n\u2009=\u2009306\u2009244; mean age 29.8 years) from Ontario, Canada. Proteinuria was defined by any of the following: urine albumin:creatinine ratio ≥3\u2009mg/mmol, urine protein:creatinine ratio ≥5\u2009mg/mmol or urine dipstick proteinuria ≥1. The main outcome measure was a diagnosis of VTE up to 24-weeks post-partum. Results A positive proteinuria measurement occurred in 8508 (2.78%) women and was more common with a history of kidney disease, gestational or non-gestational diabetes mellitus and hypertension. VTE events occurred in 625 (0.20%) individuals, with a higher risk among women with positive proteinuria [32 events (0.38%)] compared with women without proteinuria [593 events (0.20%); inverse probability-weighted risk ratio 1.79 (95% confidence interval 1.25–2.57)]. The association was consistent using a more specific VTE definition, in the post-partum period, in high-risk subgroups (hypertension or diabetes) and when the sample was restricted to women with preserved kidney function. Conclusions The presence of proteinuria in the first 20\u2009weeks of pregnancy is associated with a significantly higher risk of VTE.