Maternal thrombin generation and D-dimer levels in obesity and pregnancy: results from the maternal thrombin generation in obesity and pregnancy (MaTOPs) study.

Venous thromboembolic disease (VTE) risk increases five-fold antenatally and 14-fold during the puerperium. Obesity significantly increases this risk. The D-dimer assay and more novel Calibrated Automated Thrombogram (CAT) assay laboratory tests display potential for use in VTE risk stratification in pregnancy, although to date, research in the performance characteristics of these tests in obese and nonobese pregnant populations is limited. The aim of this study was to compare D-dimer and thrombin generation levels in obese and nonobese pregnant women. Pregnant women were recruited and categorised, as obese (BMI ≥30) or nonobese (BMI 18.5-25). Blood was collected at 26-28 weeks' gestation, 36-40 weeks' gestation and 6-12 weeks postpartum and D-dimer concentrations and endogenous thrombin potential (ETP) were determined. Student's t-test was used to analyse differences in mean D-dimer and ETP. At 36-40 weeks, obese pregnant women had higher D-dimer concentrations (P = 0.001) but lower ETP levels compared with nonobese women (P = 0.044). D-dimer was higher in nonobese than in obese women at 6-12 weeks postpartum (P = 0.026). There was no difference in mean D-dimer (P  = 0.825) and mean ETP (P  = 0.424) between obese and nonobese women at 26-28 weeks. No difference was observed in mean ETP at 6-12 weeks postpartum (P  = 0.472). ETP was lower in both obese and nonobese women postpartum than during pregnancy. D-dimer was lower in obese women but not in nonobese women postpartum. D-dimer concentrations and ETP were not significantly different during multiple time points in pregnancy and postpartum between obese and nonobese pregnant women suggesting limited utility in VTE risk assessment in obese pregnant women.