# Relationship between maternal lipid profile during the third trimester and the risk of small-for-gestational-age birth: exploring inadequate gestational weight gain as a mediator

## TL;DR

High maternal HDL-C levels in the third trimester are linked to a higher risk of small-for-gestational-age births, especially when combined with low triglycerides.

## Contribution

This study identifies a novel association between maternal lipid profiles and SGA risk, independent of inadequate gestational weight gain.

## Key findings

- High HDL-C levels were associated with a 1.54-fold increased risk of SGA infants.
- The combination of high HDL-C and low TG levels significantly predicted SGA (aRR, 1.77).
- Inadequate gestational weight gain did not mediate the observed associations.

## Abstract

Lipids play crucial roles in maternal and foetal metabolism; however, their effects on birth weight remain unclear. Moreover, the potential mediating role of inadequate gestational weight gain (iGWG) in this association remains unexplored. The objective of this study was to assess maternal lipid profiles in the third trimester and their associations with the risk of small-for-gestational-age (SGA) infants, focusing on the combined effects of high-density lipoprotein cholesterol (HDL-C) and triglycerides (TG). This study also examined whether iGWG influenced this relationship.

Data were sourced from the Tongji Maternal and Child Health Cohort. Maternal fasting lipid levels were measured during the third trimester and birth information was retrieved from medical records. Log-Poisson regression analysis was performed to assess the relationship between lipid tertiles and SGA risk. The possible mediating role of iGWG was examined using the mediation package in R.

An increased risk of SGA was associated with high HDL-C levels (adjusted relative risk [aRR], 1.54; 95% confidence interval [CI], 1.15–2.07), particularly among mothers with high HDL-C and low TG levels (aRR, 1.77; 95% CI, 1.10–2.87). This association remained significant among individuals with normal pre-pregnancy weight. The relationship between lipid profiles and SGA was independent of iGWG.

An increased risk of SGA was associated with high maternal HDL-C levels. The combination of low TG and high HDL-C levels was identified as a significant predictor of SGA. iGWG did not explain these associations.

The online version contains supplementary material available at 10.1186/s12944-026-02865-x.