Large for gestational age is used to describe newborn babies who weigh more than usual for the number of weeks of pregnancy. Babies may be called large for gestational age if they weigh more than 9 in 10 babies (90th percentile) or more than 97 of 100 babies (97th percentile) of the same gestational age. This is based on U.S. statistics from 1991. About 1 in 10 babies born at 40 weeks' gestation in the U.S. in 1991 weighed more than 8 pounds, 13 ounces (4,000 grams) at birth. Three in 100 babies weighed more than 9 pounds, 11 ounces 4,400 grams).
Babies born earlier than 40 weeks are considered LGA at lighter weights. Babies born after 40 weeks are considered LGA at slightly higher weights. Overall, babies born in the U.S. in recent years weigh a little more than they used to. Normal ranges for birth weight may also be different, based on ethnic background.
Some babies are large because their parents are large. Parents may pass along this trait to their children. A high birth weight can also be related to the amount of weight a mother gains during pregnancy. Women who gain a lot of weight during pregnancy often give birth to babies who are large for gestational age.
Diabetes in the mother is the most common cause of babies who are large for gestational age. When a pregnant woman has high blood sugar, she can pass that along to her baby. In response, the baby's body makes insulin. All the extra sugar and the extra insulin that is made can lead to fast growth and deposits of fat. This means a larger baby. It also means a risk for low blood sugar right after birth. At that point, the mother's supply is no longer there, but the baby's insulin levels stay high.
If a baby is too large to fit through the birth canal easily, birth can be difficult. Problems at birth may include:
Many large babies are born to mothers with diabetes. Poor control of blood sugar may cause problems such as:
Babies who are large for gestational age may also be more likely to have yellowing of the skin, eyes, and mucous membranes (jaundice).
Babies may be called large for gestational age if they weigh more than 9 in 10 babies or 97 of 100 babies of the same gestational age. In the U.S., this means babies born at 40 weeks' gestation who weigh more than 8 pounds 13 ounces (4,000 grams) or 9 pounds, 11 ounces (4,400 grams) at birth.
Babies with this problem are often diagnosed before birth. During pregnancy, a baby’s size can be guessed in different ways. The height of the top of a mother’s uterus can be measured from the pubic bone. This measurement in centimeters usually links with the number of weeks of pregnancy after the 20th week. If this measurement is high for the number of weeks, the baby may be larger than expected. Before the baby is born, doctors use the term fetal macrosomia instead of LGA.
Other ways to check the baby’s growth before birth include:
Babies are weighed within the first few hours after birth. The weight is compared with the baby's gestational age and recorded in the medical record.
Treatment will depend on your child’s symptoms, age, and general health.
If ultrasound exams during pregnancy show that your baby is very large, your healthcare provider may recommend early delivery. You may need a planned cesarean section.
After delivery, a baby who is large for gestational age will be carefully checked for any injuries that happened during birth. Your baby may have blood glucose testing for at least the first 12 hours to check for low blood sugar.
Babies who are large for gestational age are at higher risk for a breathing problem called respiratory distress syndrome. They also may be at risk of breathing meconium into the lungs around the time of delivery.
Birth injuries such as a broken collar bone or damaged nerves in the arm (brachial plexus) are more common in babies who are very large for gestational age. These babies also may need to stay in neonatal intensive care because of breathing problems, low blood sugar (hypoglycemia), or both. The risk for problems increases as the birth weight increases. This is especially true for babies who weight more than 9 pounds 15 ounces (4,500 grams).
LGA babies are more likely to have an excessive amount of red blood cells (polycythemia). As these red blood cells break down, their livers may not be able to handle the increased about of bilirubin needing to be conjugated. This may result in high levels of bilirubin in the blood resulting in jaundice.
Tips to help you get the most from a visit to your child’s healthcare provider:
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