Statistical analyses
Maternal demographic characteristics and clinical factors were compared between venous thrombosis cases and control groups. Continuous variables were described by mean with standard deviation (SD) or median with interquartile range (IQR). Categorical variables were described by frequencies (%). Analysis of variance or Kruskal-Wallis H tests were performed for continuous data, and chi-square tests or Fisher’s exact tests were performed for categorical data.
Multivariate log-binomial regression models were used to estimate the adjusted odds ratios (aORs) and 95% confidence intervals (CIs) for separately PE alone, DVT (including DVT and concomitant PE) and all VTE events across GWG in different periods of pregnancy. Regression model were adjusted for only co-variables with p <0.2 (maternal age, parity, ART, delivery mode, fetal number, birthweight, PIH, GDM and postpartum hemorrhage). Interaction effects between GWG and other covariates (parity, birthweight, maternal age and delivery mode) on venous thrombosis were also tested.
All analyses were performed using the Statistical Analysis System (SAS) for Windows, version 9.4 (SAS Institute, Cary, NC). P<0.05 was considered statistically significant.