Effect of using population-specific body mass index cutoff points in the risk assessment of pregnant Asian women for venous thromboembolism.

Introduction: Current international Royal College of Obstetricians and Gynaecologists (RCOG) guidelines list maternal obesity (body mass index [BMI] ≥ 30.0 kg/m2) as a risk factor for venous thromboembolism (VTE). Although the World Health Organization (WHO) has recommended lower BMI cutoff points for Asians when risk stratifying for diseases associated with obesity, this has not been extended to maternal obesity. In the present study, we compared the difference in using Asian-specific BMI cutoff points as opposed to those in international guidelines in determining the population at risk for VTE, as defined by RCOG guidelines.

Methods: All spontaneous deliveries (n = 94) and Caesarean sections (n = 41) over a three-week period, and instrumental deliveries (n = 15) over a two-month period, were reviewed and risk stratified based on Asian-specific, as well as international, BMI cut-off points.

Results: For the group that underwent spontaneous vaginal delivery, the percentage of patients at risk for VTE nearly doubled (from 8.5% to 16.0%) with the revised risk stratification, while that of patients who had instrumental delivery had more than a two-fold increase (250%). In the initial risk stratification of the post-Caesarean patients, none were at high risk of VTE. However, when the lower cut-off points of 27.5 kg/m2 and 23.0 kg/m2 were used, one and three patients were respectively identified to be at high risk.

Conclusion: Further research and consideration regarding the adjustment of international risk stratification guidelines to accommodate population-specific differences are required so that at-risk patients are not missed.