Small for gestational age (also known as small for gestational age and intrauterine growth retardation) is a group of newborns whose birth weight is below the 10th percentile of the mean weight of children of the same gestational age or below 2 standard deviations from the mean weight. There are preterm, full-term, and postterm infants. Full-term small sample infants (gestational age ≥37 weeks, <42 weeks) tend to have a birth weight below 2500g and are the most common among small sample infants. Small sample infants may be the result of intrauterine growth restriction, and some of them are small but healthy newborns. 1, the mother factor: short stature, small uterus, poor diet, may lead to the formation of children full-term small sample, this baby after birth, intelligence and behavior is not too big problem, reasonable feeding should not be too much difference with the same age children. 2, the placenta problem: the placenta in the wrong position, but also easy to have a certain lack of nutrition, thus leading to the child appeared full-term small sample. 3, the baby’s own problems: (1) trisomy 21: this is a genetic chromosomal disorder, but often there is a certain screening when doing amniocentesis as well as including Down’s syndrome screening. (2) some genetic metabolic system diseases, especially diabetes and the like, which can easily cause hypoglycemia. (3) Inadequate nutrition, phlegm, will easily cause this condition to occur.