Nutrition - Newborn: Nursing

The newborn’s diet must supply the calories and nutrients, including carbohydrates, proteins, fats, vitamins, and minerals needed to support the rapid growth and development that occurs in early life. During the first few months of life, newborn nutritional needs can be met by either breast milk or iron-fortified infant formula.

Alright, let's look at the composition of breast milk, which differs with each of the three phases of milk production, also known as lactogenesis. Phase I of lactogenesis starts during pregnancy and continues throughout the first few days postpartum. During this phase, the breasts produce an early version of breast milk called colostrum which is a thick yellowish fluid that is high in protein, vitamins, minerals, immune cells, and immunoglobulins like IgA, which protects the infant’s gastrointestinal tract from infections and aids in establishing normal flora. Colostrum is low in fat and carbohydrates, so it has few calories. Colostrum also has a laxative effect, which promotes the passage of the infant’s first bowel movement called meconium, which helps prevent hyperbilirubinemia. Colostrum meets all the nutritional needs for the newborn during the first few days of life.

Now, Phase II of lactogenesis starts two to three days postpartum. The milk produced during this phase is called transitional milk. Compared to colostrum it contains less immunoglobulins and proteins, but has more vitamins, fats, and carbohydrates, so it’s higher in calories.

The last phase of lactogenesis is Phase III, during which mature milk is produced. Mature milk is present by 10 days to 2 weeks postpartum, and contains nutrients that are sufficient for appropriate infant growth. These include proteins, carbohydrates, and fats, as well as vitamins, minerals, and enzymes, like lysozyme, which has antibacterial properties.

Now, the nutritional content of mature breast milk will vary during the course of the feeding session. So, foremilk, which is the first milk that flows from the breast, is rich in protein and carbohydrates, and low in fat, so it has less calories. It is also quite watery, so it quenches the infant’s thirst. On the flip side is hindmilk, which is the milk near the end of feeding. Hindmilk is rich in fat, and thus higher in calories.

In addition to the nutritional advantages of breastmilk, there are many long-term health benefits for the baby, including promoting a healthy gut microbiome, lower rates of allergies, ear infections, asthma, and sudden infant death syndrome, or SIDS. Moms can also benefit from breastfeeding, because it promotes uterine involution, reduces the risk of postpartum hemorrhage, burns calories, and reduces the risk of cancers of the breast, uterus, and ovary; as well as conditions like osteoporosis, type II diabetes, and heart disease. Finally, breastfeeding is free!