In the hospital, newborns are usually fed shortly after delivery, then ideally on demand thereafter. During the first week after birth, babies take ½ ounce to 2 ounces at a time, gradually increasing to 3 or 4 ounces about 6 to 8 times a day by the second week. Parents should not urge newborns to finish every bottle but, rather, allow them to take as much as they want whenever they are hungry. As infants grow, they drink larger amounts, consuming up to 6 to 8 ounces at a time by the third or fourth month.
The proper position for babies who are bottle-feeding is semi-reclining or sitting up. Babies should not bottle-feed lying flat on their back because milk may flow into the nose or the eustachian tubes (see Figure: The Eustachian Tube: Keeping Air Pressure Equal). Older infants who are able to hold their own bottle should not be put to sleep holding the bottle because the continuous exposure to milk or juice can damage their teeth and lead to cavities.
Commercial baby formulas are available as ready-to-feed sterile bottles, cans of concentrated formula that must be diluted with water, and powder. Formulas contain a proper balance of nutrients, calories, and vitamins and are available both with and without an iron supplement. All formula-fed babies should be given iron-fortified formula to prevent iron deficiency anemia.
Parents who use concentrated formula or powders must carefully follow the directions for preparation. Concentrated and powdered formulas should be prepared with water that has fluoride in it. Formulas are usually made from cow's milk, but other special formulas are available for infants who cannot tolerate cow's milk. If infants cannot tolerate standard formula, the pediatrician may recommend switching to a soy-based formula or a hydrolyzed formula. If infants cannot tolerate a hydrolyzed formula, they may be switched to an amino acid formula. There are no long-term health differences in infants fed either standard or special formula. Plain cow's milk, however, is not an appropriate food during the first year of life.
To minimize the infant's exposure to microorganisms, formula must be fed from a sterile container. Disposable plastic liners eliminate the need to sterilize bottles. Nipples for the bottles should be sterilized in the dishwasher or in a pot of boiling water for 5 minutes. Parents should warm formula feedings to body temperature. Filled bottles (or formula containers, if disposable liners are used) are placed in a warm water bath and allowed to come to body temperature. Babies may be seriously burned if formula is too hot, so parents need to shake the bottle gently to even out the temperature and then check the temperature by placing a few drops on the sensitive skin inside their wrist. Formula at body temperature should feel neither warm nor cold to the touch. Microwave ovens may dangerously overheat formula and are not recommended for warming formula or baby food.
The size of the nipple opening is important. In general, formula should drip slowly out of a bottle held upside down. Larger, older infants want larger volumes of liquid and can tolerate a larger nipple opening.
(See also Overview of Feeding of Newborns and Infants.)