Large for Gestational Age
A newborn, whether delivered preterm, term, or postterm, whose weight is above that of 90% of babies of the same gestational age at birth (above the 90th percentile) is considered large for gestational age.
Some newborns are large for gestational age because of genetic factors, such as having large parents. Another cause is diabetes in the mother.
If the mother has diabetes during pregnancy, a large amount of glucose (sugar) crosses the placenta and results in high levels of glucose in the fetus's blood, with the release of increased amounts of insulin. The result is accelerated growth of the fetus, including almost all organs with the exception of the brain, which grows normally. Vaginal delivery of a very large-for-gestational-age fetus may be problematic, increasing the risk of injury. Therefore, such a fetus may have to be delivered by caesarean section.
The large-for-gestational-age newborn born to a diabetic mother typically has a florid (reddish) complexion and appears obese and sometimes lethargic. Large-for-gestational-age newborns born to mothers who do not have diabetes are large, but not reddish or lethargic. After birth, when the supply of glucose from the placenta stops, the continuing rapid production of insulin leads to low levels of glucose (hypoglycemia). Often hypoglycemia produces no symptoms. Sometimes, the newborn is listless, limp, or jittery. Despite their large size, newborns of diabetic mothers often do not feed well for the first few days. Occasionally, newborns born to diabetic mothers have an abnormally high red blood cell count. As the red blood cells are broken down, bilirubin is formed, and these newborns tend to have high bilirubin levels, resulting in jaundice (see Section 23, Chapter 264).
Large-for-gestational-age newborns born prematurely to diabetic mothers are also more likely to have immature lungs and to develop respiratory distress syndrome, even when born only a few weeks before full term. They also have a higher rate of birth defects than other newborns.
Testing the amniotic fluid in mothers with diabetes before delivery can be performed to determine lung maturity and the likelihood of the newborn developing respiratory distress syndrome after birth. If labor appears imminent, a corticosteroid may be given to increase lung maturity.
To treat hypoglycemia in the newborn, intravenous glucose or frequent feedings by mouth or by tube into the stomach are often needed. Treatment of other complications, such as respiratory distress syndrome, is needed.
Large-for-gestational-age newborns born to diabetic mothers are likely to be significantly overweight later in childhood and as adults, which puts them at risk for type 2 diabetes (see Section 13, Chapter 165).
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