The biology of human drip breast milk.

The milk which drips from the opposite breast during breast feeding is used in some centres for feeding premature babies, yet there is little scientific information on the biology of this secretion. Drip breast milk (DBM) differs from expressed breast milk (EBM), both in its contents and in the change in its composition over the period of lactation. The fat concentration and energy value of DBM are low, compared with levels reported for EBM: protein, fat, sodium and energy value in DBM fall with the duration of lactation, whereas magnesium and calcium rise, and lactose, potassium osmolality and lysozyme remain constant. The milk fat content of DBM produced by individual donors is linearly related to the daily volume of DBM produced. Studies on 477 women admitted to the Oxford General Practice Obstetric Unit over 1 yr showed that, of the 75% who were lactating successfully 2 wk after delivery, 19% were producing DBM by 2--4 wk. Women who produced DBM did not differ in age or parity from those lactating women who did not, and their babies did not differ in birthweight, gestation, centile or sex. The suitability of DBM as a food for premature infants is discussed.