https://www.midwiferytoday.com/articles/kangaroocare.asp
One of the first things to happen is that maintenance of the baby's body temperature begins to depend on the mother, requiring the baby to use fewer calories to stay warm. Mothers naturally modulate the warmth of their breasts to keep their infants at the optimal temperature where babies sleep best, have the best oxygen saturation levels, the least caloric expenditure, and so forth. Maternal breast temperature can rise rapidly, then fall off as baby is warmed. As the baby starts to cool, the breasts heat up again—as much as 2 degrees C in two minutes!
Being next to morn also helps the baby regulate his or her respiratory and heart rates. Babies experience significantly less bradycardia and often, none at all. The respiratory rate of kangarooed infants becomes more stable. The depth of each breath becomes more even, and apnea decreases four-fold and often disappears altogether. If apneic episodes do occur, the length of each episode decreases. In my own experience with a baby in NICU for bradycardia and apnea, I found that both problems disappeared completely when I was home kangarooing my baby.
During kangaroo care, a premature baby's overall growth rate increases. This is in part due to the baby's ability to sleep, thus conserving energy and putting caloric expenditure toward growth. According to Dr. Ludington, during the last six weeks of pregnancy, babies sleep twenty to twenty-two hours per day. In a typical NICU, however, they spend less than two hours total in deep, quiet sleep. Most of that comes in ten or twenty second snatches. With kangaroo care, the infant typically snuggles into the breast and is deeply asleep within just a few minutes. These babies gain weight faster than their non-kangarooed counterparts, and it is interesting to note that they usually do not lose any of their birthweight.
