Fig. 4

Interaction effect between pBMI and trimester of pregnancy on serum GGT and iCAM-1 concentrations. GGT: gamma-glutamyl transferase, sICAM-1: soluble intercellular cytoadhesive molecule-1. Testing for interaction evaluates the simultaneous effect of trimester of pregnancy and pBMI on GGT (panel A) and sICAM-1 (panel B), as well and any interaction effect between trimester of pregnancy and pBMI where the effect of one variable depends on the other. Each plot displays the trimesters of pregnancy on the x-axis, the fitted values of GGT and iCAM-1 levels on the y-axis, and separate lines for each category of pBMI. Parallel lines would have indicated the absence of interaction between trimester of pregnancy and pBMI, but the presence of different slopes and nonparallel lines indicate the presence of a statistically significant interaction between trimester of pregnancy and pBMI (p = 0.05 and 0.008 respectively), indicating that the effect of trimester on the concentrations of GGT and iCAM-1 is not constant but depends on the value of pBMI