The aim of this study was to compare the breast milk compositions of mothers who delivered babies in three different birth weight categories.We collected 75 breast milk samples from mothers of small-for-gestational age (SGA), appropriate-for-gestational age (AGA), and large-for-gestational age (LGA) term infants (25 per group) on the 11th-28th day postpartum using a manual or electric breast pump. Homogenized samples were analyzed using a mid-infrared human milk analyzer within 2 hours of collection, and protein, carbohydrate (CHO), fat, and energy levels were compared.Of 75 participants (median maternal age: 29 years), there was a significant difference in maternal body mass index (BMI), gestational age, and birth weight among the three groups. However, we found no significant variation in breast milk true protein, crude protein, fat, or energy. The CHO composition of breast milk in mothers of SGA infants (7.1 g/100 mL, range: 6.6-7.3 g/100 mL) was significantly lower than that in the AGA (7.3 g/100 mL, range: 7.1-7.5 g/100 mL) and LGA (7.2 g/100 mL, range: 6.7-7.4 g/100 mL) groups. After post hoc multiple comparison, only CHO levels between the SGA and AGA groups were significantly different (p = 0.025), whereas no significant correlation was found between maternal BMI, gestational age, and CHO.The CHO component in breast milk from mothers of SGA infants was significantly lower compared with the AGA and LGA groups, but with no clinical significance. Breast milk compositions of mothers of LGA infants were comparable to those of SGA and AGA infants. Therefore, fetal growth status does not significantly influence maternal breast milk nutrients.