Effects of Infant Formula on the Growth and Tolerance in Preterm/Low Birth Weight Infants

Inclusion Criteria for Stage 1: * Less than or equal to 34 weeks gestational age at birth, and birth weight ≥ 1000g to \< 1800g; * Apgar score in 5 minutes after birth ≥ 7; * Infant is 21 days or less of age at enrollment; * Only singleton or twin births; * Infants who can receive early enteral feeding stably (reaching 50% or higher of the required daily total calories) and whose parents/guardians and investigators have selected Similac Special Care (SSC) for feeding; * Infant has been classified as appropriate for gestational age (AGA) or if classified as asymmetric small for gestational age (SGA) (Asymmetric SGA: Weight below the 10th percentile, but head circumference is greater than or equal to the 10th percentile) enrollment has been preapproved by sponsor; Inclusion Criteria for Stage 2: * Infants with birth weight \< or = 1500g, subjects whose parents/guardians and investigators have selected NeoSure for continued feeding after hospital discharge. Exclusion Criteria for Stage 1: * Serious congenital chromosomal or metabolic abnormalities that may affect growth and development; * Congenital gastrointestinal malformations , including but not limited to congenital megacolon or gastric-intestinal perforation; * Serious complications associated with preterm birth, including but not limited to necrotizing enterocolitis (NEC), septicemia or sepsis; * Other serious disorders of cardiac/respiratory/endocrine/hematological/ gastrointestinal/other systems, or serious diseases requiring surgical intervention; * Maternal incapacity: including maternal drug, cocaine or alcohol abuse during pregnancy or current; * Infants who received any experimental treatment, participated in other clinical trials or received other study interventions unrelated to this study within 30 days prior to enrollment; * Infants who have received or planned to receive breastfeeding or other infant formula (powder) other than SSC with calories intake ≥25% of the required daily total calories * Intubation for ventilation at the time of enrollment. Exclusion Criteria for Stage 2: * Infants who have received breastfeeding or other infant formula (powder) during hospitalization other than SSC with calories intake ≥25% of the required daily total calories * Infants who have planned to receive breastfeeding or other infant formula (powder) other than NeoSure after discharge with calories intake ≥25% of the required daily total calories