A prospective, multicentre, randomized, double-blind, parallel control study was conducted to analyze the changes in growth, intestinal flora, and immune function of infants with different feeding patterns from postnatal to 1 year of age.

Breast milk is the most beneficial and safe natural food for the growth and development of infants, but some mothers cannot complete breast feeding.For infants who cannot be breastfed, how to improve the composition of formula milk powder and improve the growth and development of infants is an important issue to be solved urgently in this field.It has been found that new compound functional ingredients oligosaccharides and sialic acid may be beneficial to the healthy growth and development of infants and young children, but the specific mechanism and significance are still unclear due to the lack of systematic research.Known as the "second Brain", the gut is connected to the Brain via the brain-gut-axis.Intestinal microecological status can significantly affect the development of infant nervous system and immune system, and then affect the occurrence of related diseases in adulthood.Oligosaccharides and sialic acid may affect the structure of intestinal microecology, protect the immune function of infants and promote the healthy development of infants.This project is based on the previous studies, using multicenter, prospective, randomized, double-blind, parallel-group trial, discussion of oligosaccharides and sialic acid in infants and young children the intestinal micro ecology and the regulation of immune function and the role mechanism, revealing the oligosaccharides and sialic acid in infants and young children the role of immediate and long-term growth, and the significance of these new type of composite function is added to the dairy ingredients, to research and development more accord with our country new dairy products provide theoretical basis for the healthy growth of infants and young children.

Inclusion Criteria:

1. Healthy infants;
2. Full-term (gestational age ≥37 weeks);
3. Birth weight 2500-4500g;
4. Mothers have no history of diabetes, hypertension, heart disease, and other diseases during pregnancy;
5. The guardian signed informed consent and voluntarily enrolled into the group and promised to complete systematic follow-up.

Exclusion Criteria:

1. Hospitalization with cognitive impairment or deformity ≥2 days
2. History of birth asphyxia (Apgar score < 3)
3. Severe allergy to milk and serious medical conditions such as intracranial hemorrhage, chronic diarrhea, necrotizing colitis, or acute infection
4. The guardian refused to enroll or could not complete the system follow-up.

Breastfeeding group The mother can breastfeed exclusively until the infants is at least 4 months old, after which complementary foods are added scientifically according to the baby's condition.

Formula group containing new compound functional ingredients Only use formula milk powder containing oligosaccharides, sialic acid and other ingredients feed the infants for at least 4 months, and then complementary food is added scientifically according to the infant's condition.

Formula group containing new compound functional ingredients Only use formula milk powder containing oligosaccharides, sialic acid and other ingredients feed the infants for at least 4 months, and then complementary food is added scientifically according to the infant's condition.