Objective To evaluate the associations between first trimester 25-hydroxyvitamin D [25(OH)D] status and changes in high-density lipoprotein cholesterol (HDL-c), low-density lipoprotein cholesterol (LDL-c), total cholesterol (TC), triglyceride (TG) concentrations, TG/HDL-c, and TC/HDL-c ratios throughout pregnancy. We hypothesized that first trimester 25(OH)D inadequacy is associated with lower concentrations of HDL-c and higher LDL-c, TC, TG, TG/HDL-c, and TC/HDL-c ratios throughout pregnancy. Methods A prospective cohort study with 3 visits at 5–13 (baseline), 20–26, and 30–36 gestational weeks, recruited 194 pregnant women attending a public health care center in Rio de Janeiro, Brazil. Plasma 25(OH)D concentrations were measured in the first trimester using liquid chromatography–tandem mass spectrometry. 25(OH)D concentrations were classified as adequate (≥ 75 nmol/L) or inadequate (