The first 1,000 days are crucial for health and development, as growth impairments during this period can lead to lasting health challenges. In low- and middle-income countries, undernutrition, a significant contributor to growth impairment, often coexists with rising obesity rates, resulting in a double burden of malnutrition (DBM). Our study employs a mathematical approach to examine how maternal socioeconomic status (SES) impacts child growth and nutritional status in Iranian children from infancy to age two, using Cole’s formula to evaluate SES effects on the DBM. Our findings offer new insights into strategies for tackling both undernutrition and obesity.

We used data from the PERSIAN Birth Cohort, a multicenter prospective study conducted in five cities in Iran. SES was divided into five quintiles using multiple correspondence analysis (MCA), and child growth and nutritional outcomes were assessed with eight indicators. Missing data were handled with multiple imputation (MI). We analyzed SES impacts on growth using Generalized Estimating Equations (GEE) and predicted BMI-Z from WAZ and HAZ with linear regression by SES level and age. To explore how variations in these indicators influence the risk of developing obesity, we compared HAZ-to-WAZ ratios from GEE models with WAZ-to-HAZ beta ratios from regressions to investigate obesity development. Sensitivity analyses compared MI results with complete-case analyses (CCA). All analyses were performed using Stata 17.

Of the 9,015 pregnant Iranian women enrolled, 7,169 neonates were assessed at 2, 4, 6, 12, and 24 months after excluding those lost to follow-up due to abortion, neonatal death, intrauterine fetal death (IUFD), stillbirth, or incomplete birth data. Maternal SES increasingly influences children’s WAZ with age, notably preventing underweight in higher SES groups. While SES impacts HAZ consistently, its significance is pronounced only in higher SES groups, enhancing stunting prevention. The effect of SES on WHZ intensifies with age, beginning at Middle SES and peaking in Very High SES. Higher SES groups, particularly Very High, exhibit a significant rise in obesity risk by 24 months. Comparing ratios from GEE models (HAZ contrast/WAZ contrast) and regression models (β WAZ/β HAZ), we found HAZ contrast/WAZ contrast was generally lower where BMI-Z increased. Sensitivity analysis showed that estimates from MI and CCA were consistent, confirming the robustness of SES effects on child growth.

Addressing the DBM requires careful consideration of how imbalanced increases in HAZ and WAZ can heighten obesity risk. Future research should focus on targeted interventions that account for these growth dynamics to effectively manage DBM in children.