To evaluate the rate of change in serum lipids and the factors associated with their variations, stratifying for pre-pregnancy body mass index (BMI) categories. Prospective cohort. Public Health centre, Rio de Janeiro, Brazil. Two hundred and twenty-five healthy pregnant women recruited between 2009 and 2011. Women were evaluated during the three trimesters of pregnancy (5th-13th, 20th-26th and 30th-36th gestational weeks). Pre-pregnancy BMI (kg/m²) was classified as normal weight (NW=18.5-24.9), overweight (OW=25.0-29.9) or obese (OB≥30.0). The independent variables included maternal socioeconomic, demographic, biochemical and lifestyle factors. We performed linear mixed-effects models adjusted for gestational age and body weight, reporting coefficient (β) and 95% confidence interval (95% CI). Longitudinal total cholesterol (TC),high-density lipoprotein (HDL-c), low-densitylipoprotein (LDL-c) and triglyceride (TG) measurements. OW and OB women presented higher mean TG, TC and LDL-c compared with their NW counterparts (P<0.05). The mean HDL-c concentrations were higher in NW than in OB women (P=0.03). OW and OB women presented lower serum TC (βOW =-0.014; 95% CI=-0.026 to -0.002; P=0.022; βOB =-0.015; 95% CI -0.015 to 0.001; P=0.066) and LDL-c (βOW =-0.012; 95% CI=-0.021 to -0.002; P=0.017; βOB =-0.018; 95% CI=-0.031 to -0.005; P=0.005) rates of change (mmol/l per gestational week) compared with the NW. Pre-gestational BMI was the main factor associated with the rate of changes in TC and LDL-c concentrations. Pre-pregnancy BMI was the main factor associated with the rate of change in TC and LDL-c throughout pregnancy, and OW and OB women presented lower rates of change compared with NW controls.