['To investigate if body mass index (BMI) is related to inflammatory markers and hormones in early pregnancy.', 'A prospective study with 190 pregnant women evaluated at 10 weeks when leptin, insulin, homeostatic model assessment-insulin resistance (HOMA-IR), C-reactive protein (CRP) and interleukin-6 (IL-6) were measured. Median and inter-quartile values of hormones and inflammatory markers are presented according to BMI quintiles. Spearman correlations and Kruskal-Wallis analysis of variance were implemented followed by Mann-Whitney post hoc pair-wise tests.', 'Leptin (P < 0.001), insulin (P = 0.005), HOMA-IR (P = 0.015), and CRP (P = 0.026) assumed higher and significantly median values as BMI quintiles increases, but no differences were observed for IL-6 (P = 0.859). Pair-wise comparisons among quintiles (Q) of BMI were significant for leptin (Q1 × Q3, Q1 × Q4, Q1 × Q5, Q2 × Q4, Q2 × Q5, Q3 × Q5), insulin (Q1 × Q5, Q2 × Q5, Q3 × Q5, Q4 × Q5) and for CRP (Q1 × Q4, Q1 × Q5, Q2 × Q5). Spearman correlation coefficients between BMI showed significant results for leptin (r (s) = 0.58, P < 0.001), insulin (r (s) = 0.19, P = 0.018), HOMA-IR (r (s) = 0.22, P = 0.007), CRP (r (s) = 0.26, P < 0.001), but not for IL-6 (r (s) = -0.06, P = 0.526). Median (mg/L) values of CRP were higher in overweight (35.26) than in normal weight women (21.28, P = 0.051).'] Are c-reactive protein and hormones but not IL-6 associated to body mass index in first trimester of pregnancy?