Conclusion
Our results showed that under the proper pre-pregnant BMI criteria in South China, the proportion of underweight women was nearly equal to that of overweight/obese women. Underweight women had significant higher TC level than those of normal-weight women and overweight/obese women. Moreover, underweight women with high TC level had significantly higher occurrence of LGA, and lower occurrence of SGA, while there were no significant associations between serum TC and LGA or SGA in normal-weight women and overweight/obese women. The higher TC level in underweight women could be an adaptive response to satisfy the maternal and increasing fetal demand, and we presume cholesterol may be a more significant material for maintaining pregnancy and fetal development. Moreover, considering the association between serum lipid levels of underweight women and neonate birth weight, we recommend pre-pregnant underweight women to control their serum lipid level properly for preventing the occurrence of LGA and other adverse maternal and fetal outcomes.