Newborn's Greater Risk
Blood sugar is the common name for glucose, the carbohydrate fuel the body uses for quick energy. As an unborn baby approaches the ninth month of gestation, he builds a storage form of glucose, called glycogen. These glycogen stores are critical to help carry the infant through the rigors of labor and the early hours afterward.
Stored glycogen, however, may run out too soon for some babies. A full-term infant who is stressed due to a difficult labor, infection, congenital disease, fever, abnormal birth weight or other reason may quickly run through glycogen and deplete remaining circulating blood sugar. Such a baby will run into problems with low blood sugar, or hypoglycemia.
If an infant is born prematurely, this is an even more dangerous situation for running into hypoglycemia. If she is born too early her glycogen reserves will not have developed. Without fuel to draw on, her sugar can also quickly run out without intervention.
Another reason a baby may be born with an abnormal sugar is if he is born to a diabetic mother. If the diabetes is not treated properly while inside his mother's uterus he may be exposed to abnormal levels of insulin. If his mother's diabetes was untreated, the circulating sugar he experienced was high and his own insulin had to kick in to normalize it for his own body. If mom's diabetic treatment was too aggressive, and she was given too much insulin, he may have repeatedly suffered from his own sugar being pushed down by his mother's insulin. In either extreme, once born, he may have trouble regulating sugar properly and it may jump too high or too low.
What's Normal
A baby cannot tell you, in words, how she is feeling. A newborn's body is trying to automatically adjust to breathing, maintaining blood pressure, growing new blood cells, fighting infection and regulating her chemistry for the first time on her own. Any of these things can be a big or small struggle. A newborn's normal heart rate is 120-140 beats per minute, much faster than an adult's. It is easiest to feel a baby's heartbeat by placing one or two fingers gently around the new belly button--or you can use a stethoscope to listen over her chest.
Low Blood Sugar
Low blood sugar in a new baby can sometimes only be noted as an abnormal heart rate. Newborns usually respond to low blood sugar with a speeded up heart beat, just as do children and adults.
Low blood sugar increases most infants' heart rates for the same reason anyone will find a racing heart with hypoglycemia. As soon as the body recognizes the low blood sugar, it floods the blood stream with adrenalin. Adrenalin races to the liver and muscles to get them to release any glucose available. Adrenalin is the "fight or flight" chemical and pumps the heart rate up as a side effect.
However, very ill, premature or very large birth weight babies may have low blood sugar yet an abnormally slow heart beat instead. This can be because the very sick baby cannot respond to adrenalin or is even too ill to produce it.
Helping Hypoglycemia
If a new baby is healthy but his heart beat is abnormal, one of the quickest, safest things is to offer him breast milk, sugar water or formula right away and see if he improves. This is one of the best arguments for nursing right after birth, to forestall any problems with low sugar. If a baby is too ill or this does not fix the problem within minutes, any of these heart rates should signal an immediate need to check a blood sugar level, because overlooking a very low blood sugar in an infant can cause seizures, brain damage or even death. While waiting for results, a baby suspected of serious hypoglycemia can be treated with sugar water given through a vein or artery.
High blood sugar can also alter a newborn's heart rate slightly, but this is hardly ever significant. Congenital conditions exist, but it is hypoglycemia which is sometimes only revealed in an abnormal heart rate.
