1. Introduction
Thromboembolism in pregnancy is among the leading causes of maternal morbidity and mortality, worldwide [1-4]. In pregnant women, venous thromboembolism (VTE) presents as deep vein thrombosis (DVT) or pulmonary embolism (PE). It is well recognized that pregnancy increases the risk of thromboembolism under conditions of hypercoagulability, decreased mobility, and compression of the inferior vena cava and pelvic veins. In recent decades, VTE has become a leading cause of sudden death, accounting for 15-30% of all maternal deaths in the United States and other Western countries [5-6]. Therefore, VTE in pregnancy is an emerging health issue, and there is an urgent need to estimate its prevalence profile.
The reported incidence of thromboembolism in pregnancy greatly varies. Across different hospital settings, the rate of VTE diagnosis ranged from 1 in 500 to 2,000 pregnancies in the United States [7-8]. Hospital organizational factors such as VTE prevention, diagnosis and treatment potentially affect the disease’s incidence in pregnant women. With the use of proper preventive mechanical prophylactic devices and anticoagulants for high-risk pregnant women, the rate of maternal death due to thromboembolic disease had declined from 14.8% in 2006 to 3.2% in 2014 [9-10]. Additionally, considering the fact that there is an overlap between the symptoms of VTE and pregnancy, the early detection of VTE and the method used for the same influence the related diagnoses. Second, the incidence of VTE varies across different patient backgrounds: Asian women show a lower risk of VTE and death from VTE than black women in the United States [11-12]. Third, the incidence values varied across different epidemiological studies. In a retrospective case-control study in United Kingdom, the incidence of VTE was 0.85 per 1000 pregnancies [13], while in a population-based cohort study in the United States, the incidence was 2 per 1000 pregnancies [14]. Thus, the incidence of VTE in pregnancy is influenced by hospital-related variations due to differences in the healthcare settings, diagnosis competency, and patient heterogeneity.
Given the marked diversity of hospital settings across China, we hypothesize that the incidence of thromboembolism in pregnancy significantly varies in different hospitals. In order to investigate the status of VTE in China, and identify hospital organizational factors affecting its incidence, we performed a hospital-based point prevalence survey in 113 hospitals throughout China.