Colostrum will gradually change to become mature milk.

Mature milk, which has more fat and less protein than transitional milk, starts being produced about 10 to 15 days after the baby is born.

Weight gain is more rapid after mature milk is produced, about 10 to 15 days after you deliver your baby.

The transitional milk comes in after the colostrum, followed by mature milk about 10 to 15 days after you deliver your baby.

The colostrum usually tastes a little different than mature milk, so you may find your baby not as interested in this new menu item and starting the process of weaning."

Concentration of lactoferrin in the milk varies from 7 g/L in the colostrum to 1 g/L in mature milk.

Mothers delivering before full term may not have adequate mammary development, and may not reach full mammary development by the time they begin producing mature milk.

It contains higher amounts of white blood cells and antibodies than mature milk, and is especially high in immunoglobulin A (IgA), which coats the lining of the baby's immature intestines, and helps to prevent pathogens from invading the baby's system.

This is spelled out in Breastfeeding for Dummies by Sharon Perkins, RN, and Carol Vannais, RN: "Somewhere between four and eight months of pregnancy, your milk does start changing from mature milk back to colostrum, the first type of milk that you gave your baby.