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