Most are related to various factors that lead to placental dysfunction, such as pregnancy-induced hypertension syndrome, chronic hypertension, pregnancy-related infections (e.g., rubella, cytomegalic inclusion disease, toxoplasmosis), chronic heart and kidney diseases, cyanotic cardiovascular abnormalities, early marriage and first childbirth, twins, elderly multiparous women, tobacco and alcohol addiction, severe malnutrition, vitamin A deficiency, lack of folic acid during pregnancy, high-altitude regions, use of adrenocortical hormones or other immunosuppressive drugs, prolonged use of tetracycline or antimetabolic drugs in late pregnancy, abnormal umbilical cord attachment sites, single umbilical artery, congenital malformations, chromosomal abnormalities, and other factors that can cause fetal malnutrition and hypoxia. Research data show that the oxygen content and oxygen saturation percentage in the umbilical vein indeed decrease with the severity of growth-restricted infants (grade III), but are unrelated to gestational age.

bubble_chart Treatment Measures

Small-for-gestational-age infants must be treated as "high-risk" newborns, with special attention paid to the following aspects:

1. Further investigate the mother's nutritional status during pregnancy, diseases, smoking and drinking habits, family history of genetic metabolic disorders, exposure to toxic substances, pregnancy history, etc., to trace potential disease causes and serve as a reference for management.
2. Preparations for resuscitation should be made before delivery.
3. At birth, handling and resuscitation must be performed in a warm environment above 30°C. During transport from the delivery room, continuous warmth must be maintained, preferably by dressing the infant in pre-warmed clothing and using a portable incubator. In some countries, aluminum foil wrapping is used to prevent heat loss. After admission to the neonatal unit or rooming-in with the mother, the infant’s body temperature should be stabilized at 35°C as soon as possible. The goal is to conserve energy, as these infants have reduced liver glycogen stores and impaired gluconeogenesis.
4. After resuscitation or if respiratory distress and cyanosis are present, oxygen therapy should be administered promptly.
5. Early feeding is an effective measure to prevent hypoglycemia. Due to their higher metabolic rate compared to premature infants of the same weight, their caloric needs are greater. Infants with strong sucking ability should ideally breastfeed directly on demand. Alternatively, expressed breast milk can be spoon-fed or administered via nasogastric tube. For infants with low birth weight, insufficient oral intake, or those unable to achieve 251.0 kJ (60 kcal)/kg/day within the first 3 days or 502.1 kJ (120 kcal)/kg/day by day 10, intravenous glucose or parenteral nutrition may be supplemented.
   Early and adequate feeding not only prevents hypoglycemia and promotes weight gain but also supports the proliferation of glial cells in the brain, reducing the risk of intellectual disabilities and other sequelae. Neurological development in early pregnancy involves an increase in the number of neuronal cells, while the late stage (third trimester) primarily involves neuronal enlargement, axonal branching, and myelination. Thus, adequate nutrition in the early postnatal period is critical for brain development. Since these infants often exhibit asymptomatic hypoglycemia, or symptoms may be nonspecific and mistaken for other causes, regular blood glucose monitoring is essential. If levels fall below 2.22 mmol/L (40 mg/dL), administer 25% glucose intravenously at 2–4 mL/kg, followed by a 10–12% glucose infusion to maintain normal blood glucose for 24–48 hours. Gradually taper the infusion once oral intake can sustain normal glucose levels, but continue monitoring blood glucose for 3 days to prevent recurrence.
6. **Prevention and Treatment of Other Complications:** - Correct acidosis early in cases of hypoxia or asphyxia. - Administer intravenous calcium gluconate for hypocalcemia. - Perform exchange transfusion for symptomatic polycythemia. According to research by the Shanghai Pediatric Medical Institute, these infants often have lower blood zinc levels than normal infants. Therefore, zinc supplementation (3 mg daily for 6 months) is recommended to prevent anorexia, which could lead to further malnutrition and developmental delays.
7. Infection prevention is also crucial. If intrauterine infection is suspected, umbilical cord blood IgM testing and TORCH screening should be performed. Additional evaluations, such as skull X-rays, ultrasound, CT scans, chromosomal analysis, and fundus examinations, may be necessary.
8. Intelligence training can promote neurological development and improve IQ. Long-term follow-up and feedback help refine perinatal and neonatal management strategies.