Objective: To determine the relationship between lipid profile and risks of adverse pregnancy outcomes in pre-pregnant underweight women. Design: This study was part of an ongoing cohort study which Chinese gravidas delivered from January 2015 to December 2016. Setting: Pre-pregnant body mass index (pre-BMI) was classified into underweight (<18.5 kg/m2)， normal weight (18.5-22.9 kg/m2) and overweight/obesity (≥23 kg/m2). Population: There’re 1203 underweight- women, 3281 normal-weight women and 1209 overweight women met the criteria. Methods: Data of 6233 women and medical information including lipid concentrations, pregnancy complications, pregnancy and perinatal outcomes were analyzed. Results: The proportion of underweight women 19.2% and overweight/obese women19.4% was similar in South China. Serum TC level of underweight women was significantly higher than overweight/obese women (p < 0.001). After adjusting for maternal age, underweight women with high TC level had significantly higher occurrence of LGA [OR=2.24, 95%CI (1.08, 4.63)], and lower occurrence of SGA [OR=0.71, 95%CI (0.59, 0.85)], while there were no significant associations between TC and LGA or SGA in other groups. Conclusion: Underweight women with high TC had higher occurrence of LGA, while there was no association between TC levels and LGA in normal and overweight/obese women. Thus, we should recommend underweight women to manage the lipid. Funding: This work was supported by the National Natural Science Foundation of China (Grant No: 81771606), Shenzhen Science and Technology Innovation Commission (Grant No: JCYJ20170817172241688, JCYJ20180228163459314), and Clinical Medical Project 5010 of Sun Yat-sen University, China (Grant No: 2012004). Key words: underweight; cholesterol; LGA; overweight;