Impact of perinatal factors on breast milk composition and volume in preterm infants

Maternal age, type of delivery, and newborn sex can influence the volume and composition of human milk (HM) expressed by mothers of premature infants. Initiating and maintaining breastfeeding in these mothers is a significant challenge, and records of milk volume expressed during the first few days are crucial for sustaining adequate production. To assess HM production in mothers of preterm infants during the first 15 days of life, examining the relationship between production, type of delivery, and maternal age. Additionally, we aim to analyze the macronutrient composition of HM based on various factors, such as the infant's sex, type of delivery, and maternal age. This is a prospective longitudinal study conducted over 2 years, evaluating HM production and macronutrient composition in 45 mothers of 52 premature infants born at ≤ 32 weeks of gestational age and/or weighing ≤ 1500 g, admitted to the NICU of the University Clinical Hospital of Santiago de Compostela, a Level III Q3+ facility. The study focused on the first 15 days of life, recording the volume of milk expressed and collecting milk samples on days 3, 7, and 15 for nutritional analysis of macronutrients. The study examined the influence of maternal age, type of delivery, and newborn sex on these factors. Vaginal deliveries and maternal age < 35 years were associated with a trend toward greater volumes of milk expressed compared to cesarean deliveries and maternal age ≥ 35 years. If the amount of HM expressed on day 4 was less than 140 mL/day, it significantly predicted a total expression of < 500 mL/day by day 15. We found that 64.3% of our sample expressed less than 140 mL/day on day 4, and 73.8% of these mothers did not reach 500 mL/day by day 15. Regarding macronutrients, HM contained more fat following vaginal delivery compared to cesarean delivery, with significant differences observed on day 3 of life. No differences were observed based on maternal age or newborn sex. In conclusion, HM production on day 4 is a good predictor of production by day 15; maternal age and cesarean delivery seem to negatively influence HM production; the composition of HM shows higher fat content in the colostrum of mothers who had vaginal deliveries.