The Effects of Breast Milk Versus Formula Feeding on Infant Growth: A Quantile Regression Approach

The foods that the baby receives during early life impact the health and physical growth of the newborn. This study aims to employ statistical methods such as quantile regression (QR) to examine the effect of breast milk (BF) versus formula feeding (FF) and mixed feeding (MF) on infant growth outcomes, especially weight and height. We used 207 infants of 48 months in Sulaimani City with general information about their parents as sample data, and the mode of delivery is between 38 and 40 weeks, classified by gender and feeding types. Growth metrics were measured against the World Health Organization (WHO) growth standards for children from 0 to 48 months. The QR revealed that BF supports steady and balanced growth across percentiles, with minimal gender-based differences. FF and MF were associated with increased growth outcomes at certain ages but demonstrated greater variability, particularly among female infants. Furthermore, multinomial logistic regression (MLR) indicated a significant link between Caesarean delivery and a reduced likelihood of exclusive breastfeeding, and no associations were found between parental information and choosing feedings. The body mass index (BMI) for infants compared to WHO-BMI Z-scores is normal and healthy growth, which suggests that the infants across different ages and feeding types are in normal growth, except for the FF boys at 15 months being above the median and in +1 SD, which suggests an overweight risk. These findings emphasize the nutritional and developmental advantages of BF and highlight the importance of encouraging breastfeeding practices through evidence-based health policies.