Breast milk production, or lactogenesis, is initiated during the last trimester of pregnancy. Milk begins to form, and the lactose and protein content of milk increases.Nursing during the first few weeks of a baby’s life is especially important because the early milk is loaded with nutrition and ingredients that help the immune system.

Mothers do everything they can to care for their baby’s needs. Breast milk is
really a biological extension of this maternal care, and the mother herself got many benefits in return.

Lowers your cancer risk. Women who breast-feed have lower incidences of breast, uterine, and ovarian cancers. Lactation lowers estrogen levels in the body, and lifetime exposure to estrogen is a risk factor for these cancers. The longer you nurse, the more the benefit.

Lowers your risk of osteoporosis. Breast-feeding increases bone density, reducing the risk of osteoporosis and fractures in older women who have breast-fed.

Helps you in weightloss. Nursing takes energy—about 500 calories a day, to be exact. When breast-feeding, your body is working overtime and will return to its pre-pregnancy weight more rapidly and without reducing the amount you eat.
This is estimated using the factorial approach whereby the cost of milk production is added to the energy requirement of nonpregnant, nonlactating women. Milk production cost is based on a mean milk production of 780 mL=day, energy density of milk of 0.67 kcal=g, and energetic efficiency of milk synthesis (conversion of maternal dietary energy to milk energy) of 80% . In well-nourished women, 170 kcal=day is deducted to account for energy mobilization (0.8 kg=month) from adipose stores laid down during pregnancy.
Beyond 6 months postpartum, weight loss is considered minor and total energy cost of milk production is derived solely from diet. Using a reduced milk production volume of 600 mL, recommended energy intake for partially breastfeeding women in the second 6 months of lactation is 400 kcal=day above the nonpregnant, nonlactating energy requirement.

Helps your child from being obese. Several studies have suggested that infants who are formula-fed are more likely to become obese later in life. A study of fifteen thousand children of participants in the Nurses’ Health Study II at Harvard found that children who were mostly or exclusively breast-fed for the first six months of life had a lower risk of being overweight than children who were mostly or exclusively fed formula.

There are also many other benefits for both, mom and the baby.