A newborn, whether delivered preterm, term, or postterm, whose weight is above that of 90% of newborns of the same gestational age at birth (above the 90th percentile) is considered large for gestational age.
Diabetes in mothers is the most common cause of large-for-gestational-age newborns. Women who are obese or who have previously had a large infant are also at risk of having large-for-gestational-age newborns. Some newborns are large for gestational age because of genetic factors, such as having rare syndromes (for example, Beckwith-Wiedemann syndrome or Sotos' syndrome).
The reason for excessive growth of the fetus varies but primarily results from an abundance of nutrients. In pregnant women with diabetes, a large amount of sugar (glucose) crosses the placenta (the organ that connects the fetus to the uterus and provides nourishment to the fetus) and results in high levels of glucose in the fetus's blood. The high levels of glucose trigger the release of increased amounts of insulin from the fetus's pancreas, resulting in accelerated growth of the fetus, including almost all organs except the brain, which grows normally.
Symptoms and Complications
Symptoms depend on which complications occur. Common complications include the following:
Infants whose mother has diabetes also have a higher rate of birth defects than other newborns. Large-for-gestational-age newborns born to mothers with diabetes are likely to be significantly overweight later in childhood and as adults, which, along with their genetic predisposition, puts them at risk of developing type 2 diabetes (see Diabetes Mellitus (DM): Type 2).
To treat hypoglycemia in newborns, glucose given by vein (intravenously) or frequent feedings by mouth or by tube into the stomach are often needed. Treatment of respiratory distress syndrome may require supplemental oxygen through a tube placed in the nose or intense intervention, such as respiratory support with a ventilator. Other complications may also require treatment, such as phototherapy for jaundice.
Last full review/revision February 2009 by Arthur E. Kopelman, MD