Oxidative status in colostrum and mature breast milk related to gestational age and fetal growth.

Introduction: The effect of gestational age and fetal growth on the oxidant/antioxidant status of breast milk is poorly understood.

Objective: To evaluate the oxidative stress biomarkers in colostrum and mature milk according to gestational age and fetal growth.

Method: A longitudinal study with mothers of premature and term infants, born in a tertiary referral hospital between 2014-2018. Inclusion criteria: postpartum women with a singleton pregnancy, who intended to exclusively breastfeed. Exclusion criteria: maternal diabetes, use of medication, drug addiction, congenital infection or malformation, mastitis, and failure to collect colostrum. Four groups were formed according to gestational age and birth weight (appropriate and small): Preterm small ( = 37), Preterm appropriate ( = 99), Full-term small ( = 65), and Full-term appropriate (control,  = 69). The colostrum samples were collected between 24-72 h and the mature milk was sampled in the 4th week of lactation for malondialdehyde (biomarker for lipid peroxidation) and Glutathione peroxidase, Catalase, and Superoxide dismutase measurements. The data were compared among groups using the Chi-square test or Fisher's exact test, one-way analysis of variance followed by Wald's Distribution test and repeated measures analysis of variance.

Results: We found a lower malondialdehyde level in colostrum in preterm groups and term small for gestational age, and the antioxidant enzymes Superoxide dismutase and Catalase activities were higher for preterm compared to term groups. The malondialdehyde levels differed in mature milk samples (Full-term small > Full-term appropriate > Preterm small > Preterm appropriate). The malondialdehyde levels increased during lactation in all groups except Preterm appropriate, and the levels of Catalase decreased in preterm groups.

Conclusion: The oxidative status in breast milk is influenced by gestational age and fetal growth, which increased antioxidant defense for preterm infants and decreased oxidative stimuli for small for gestational age infants. These findings contribute to encouraging breastfeeding for newborns.