Causes of Hypoglycemia in a Newborn

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Hypoglycemia, or low blood sugar levels, is not uncommon in newborns, affecting 2 out of 1,000 babies, the Medical University of South Carolina reports. Many newborns have transient hypoglycemia after birth. There are many causes of neonatal hypoglycemia; some are mild and transient, while others are more complicated and potentially dangerous. Hypoglycemia in newborns is defined as blood glucose (sugar) below 40 milligrams per deciliter (mg/dL).

Maternal Diabetes

Pregnant women who have diabetes prior to pregnancy or who develop gestational diabetes often have large, or macrosomic, babies. Although these babies may look exceptionally plump and healthy, they actually have more health issues than babies born to nondiabetic moms. Because they received higher than normal glucose levels during pregnancy, they gained more weight than average, and became used to higher levels of glucose in the blood. After birth, when maternal glucose disappears and the infant is on his own for making glucose, levels drop. The infant becomes hypoglycemic. Babies born to diabetic mothers may temporarily need extra glucose to keep their blood sugar levels high enough to supply energy to their brains.


Premature babies become hypoglycemia for a number of reasons. Preemies don’t have much glycogen, which converts to glucose, stored in their liver, muscles or heart, the University of Virginia explains. After birth, they quickly use up their limited stores and become hypoglycemic unless treated with glucose solutions to maintain energy levels. Premature babies also become cold easily, which also uses up more glucose than normal, and undergo stressful procedures, which further increases the demand for glucose. Preterm babies are also more prone to infection, another potential cause of increased glucose use. Lastly, preterm babies have immature livers that don’t synthesize enough glucose to meet their often elevated needs.

Infection and Illness

Newborns who have infections or other illnesses need more glucose than normal to fight off the infection or illness. Glucose stores in sick babies get used up quickly, leading to hypoglycemia unless supplemental glucose is given. Respiratory distress, hypothyroidism and congenital heart problems can cause hypoglycemia in newborns, the Children’s Hospital at UCSF Medical Center states.

Intrauterine Growth Retardation

Babies who are small for their gestational age, also known as intrauterine growth retardation (IUGR), also lack glycogen stores to supply their energy needs. They may need glucose supplementation to make sure their glucose levels don’t drop after birth.