OBJECTIVE. Neonatologists consider early feeding at the breast to be too tiring for preterm infants, although there is no evidence that this is actually the case. It is also not known whether the method of feeding affects energy expenditure. We hypothesized that resting energy expenditure (REE) would be higher after breastfeeding than after bottle feeding.

PATIENTS AND METHODS. preterm ( >32 weeks GA) stable infants who are nourished entirely by their mothers' breast milk will be studied when fed expressed breast milk either by bottle or at the breast. REE will be measured for 20 minutes after feeding. Breast milk quantity is evaluated by pre- and post feeding weighing.

Most VLBW infants cannot be fed at the breast upon birth, and expressed breast milk by gastric tube is thus recommended. Sucking skills mature at around 34 weeks when nipple-feeding is introduced. In the absence of evidence-based data to decide the best timing to introduce breastfeeding, many clinicians use empiric criteria, such as the infant's weight, gestational age, and the ability of infants to bottle feed as proxies of readiness to breastfeed. Despite some evidence of physiological benefits of preterm infants feeding at the breast, many neonatologists consider direct breastfeeding to be too fatiguing for preterm infants. It is not known, however, whether preterm infants who are breastfed expend more energy than bottle-fed infants

Inclusion Criteria:

• Thermally stable infants were nursed in an open and unwarmed bassinet.
• All fed solely by their mothers' breast milk equivalent to at least 150 cc/kg/day divided into eight meals and growing steadily

Exclusion Criteria:

• Infants with congenital anomalies and infants who had either more than five daily episodes of apnea of prematurity or any apnea requiring assistance or methylxanthine therapy

Preterm infants born after 32 weeks of gestation, when they reached the corrected gestational age of 34 weeks or more.