Large for gestational age (LGA) is how health professionals describe newborns who weighing more than the usual amount for the number of weeks of pregnancy. Babies are called LGA if they weigh more than 90 percent of all babies of the same gestational age.
The average baby weighs about 7 pounds at birth. About 9 percent of all babies weigh more than 8 pounds, 13 ounces (4,000 grams). Rarely do babies weigh over 10 pounds.
Although most LGA babies are born at term (37 to 41 weeks of pregnancy), a few premature babies may be LGA.
Some babies are large because their parents are large. Babies may inherit this trait from their parents. A high birthweight can also be caused by the amount of weight a mother gains during pregnancy. Women who gain a lot of weight during pregnancy often give birth to LGA babies.
Diabetes is the most common cause of LGA babies. 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 production can lead to fast growth and deposits of fat, thus, a larger baby.
Because LGA babies are so large, delivery can be difficult. Delivery problems may include the following:
Prolonged vaginal delivery time
Increased risk of cesarean delivery
Because many large babies are born to diabetic mothers, many problems of LGA babies are caused poor regulation of blood sugar. Some of these problems are:
Hypoglycemia (low blood sugar) in the baby after delivery
A higher number of birth defects
Difficulty breathing (respiratory distress)
Many babies with LGA also have jaundice or yellowing of the skin, eyes, and mucous membranes (hyperbilirubinemia).
During pregnancy, your health care provider can figure out what your baby weights by using a couple different ways. One way is to measure the height of the fundus (the top of a mother's uterus) from the pubic bone. The number of centimeters measured is usually the same or close to the number of weeks of pregnancy. If the fundus measurement is high for the number of weeks, the baby may be larger than expected. Other ways to check the baby’s growth are:
Ultrasound. Your health care provider uses sound waves to create a picture of your baby and the inside of your body. It is a more accurate method of estimating the size of your baby. Measurements can be taken of your baby’s head, belly, and upper leg bone to see how fast he or she is growing.
Weight gain during can also affect your baby's size. Gaining a lot of weight during pregnancy may cause your baby to be bigger than normal.
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.
Specific treatment for large for gestational age will be determined by your baby's health care provider based on:
Your baby's gestational age, overall health, and medical history
How sick he or she is
How well your baby handles specific medications, procedures, or therapies
How long the condition is expected to last
Your opinion or preference
If ultrasound examinations during pregnancy show a fetus is quite large, some doctors may recommend early delivery. In this case, a planned cesarean delivery may be recommended.
After delivery, a LGA baby will be carefully checked for any birth injuries. Blood glucose testing is also done to check for hypoglycemia.
Regular prenatal care is important in all pregnancies. Regular checkups can help your health care provider find out if your baby is too small or too large. If your baby seems large, it may be a sign that you have undetected diabetes or other problems. Taking care of your diabetes, watching your weight, and following your health care provider’s recommendations can help lower some of the risks to your baby.