I. Definition.
A newborn whose birth weight and/or length is below the -2nd SD or 3rd percentile of normal reference values for the same gestational age.
Incidence: 3-10% in human fetuses, 7.5% in China.
II. Etiology.
Maternal factors: such as the mother infected with diseases during pregnancy; get chronic diseases (hypertension, anemia); unhealthy lifestyle (smoking, alcohol and drug abuse, etc.); poor nutrition during pregnancy; other: influenced by the mother’s age, height, weight and race.
Placental factors: placental insufficiency, infarction, placental abruptio, vascular malformation.
Fetal factors: chromosomal or other genetic defect diseases; congenital malformations, intrauterine viral or bacterial infections, multiple births, etc.
Third, clinical features.
1. Catch-up growth and short stature
Fetal to early postnatal pediatric growth is mainly regulated by the nutrient-insulin-insulin-like growth factor metabolic axis; growth of young children after 1 to 1.5 years of age is regulated by the growth hormone/insulin-like growth factor axis, and catch-up growth of SGA is mainly regulated by the GH/IGF-I axis; most children with SGA have spontaneous catch-up growth after birth; catch-up growth starts in the month immediately after birth and reaches its maximum within 6 months Most children with SGA have spontaneous postnatal catch-up growth; catch-up growth starts immediately after birth and reaches its maximum within 6 months; most of the height usually reaches normal by 2 years of age; while about 10% of children with SGA do not show catch-up growth, resulting in a height below -2SD of the normal mean in childhood and adulthood; short stature caused by SGA accounts for 20% of short stature in adults.
2. Metabolic abnormalities: insulin resistance and metabolic syndrome
Insulin resistance (IR) exists in childhood in SGA
SGA are at high risk of developing metabolic syndrome (MS) in adulthood: type 2 diabetes, hypertension, hyperlipidemia and obesity.
The incidence of MS in adulthood is 7 to 10 times higher in SGA than in AGA
3. Intellectual and psychological abnormalities
Children with SGA are generally short and thin, with protruding faces, small jaws, small arms and legs and pelvis, and a relatively large ratio of arms and legs to body length; they may have clumsy movements, intellectual and bone age backwardness, cognitive impairment (such as poor academic and work performance); psychosocial dysfunction (such as lack of self-confidence, poor self-awareness, social apprehension, behavioral problems, etc.).
IV. Treatment.
SGA was first treated with growth hormone in 1970; the US FDA approved SGA as one of the indications for growth hormone in July 2001; the European EMEA approved it in March 2003; recombinant human growth hormone (rhGH) is used for the long-term treatment of children with SGA dwarfism who fail to achieve catch-up growth at age 2.
V. Recombinant Human Growth Hormone (rhGH) Purpose.
1. To promote linear growth before puberty and normalize height in early childhood.
2. Maintain normal height in late childhood (adolescence).
3. Achieve normal adult height.