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Large-for-Gestational-Age (LGA) Newborn

By

Arcangela Lattari Balest

, MD, University of Pittsburgh, School of Medicine

Last full review/revision Apr 2021| Content last modified Apr 2021
Click here for the Professional Version

A newborn who weighs more than 90% of newborns of the same gestational age at birth (above the 90th percentile) is considered large for gestational age.

  • Newborns may be large because the parents are large or because the mother has diabetes or is obese.

  • Doctors take measurements of the mother's abdomen and use ultrasonography to take measurements of the fetus to help estimate the fetus's weight.

  • Large babies born to mothers with diabetes are more likely to be overweight as adults.

  • Cesarean delivery is sometimes necessary.

  • Complications are treated.

Gestational age refers to how far along the fetus is. The gestational age is the number of weeks between the first day of the mother's last menstrual period and the day of delivery. This time frame is often adjusted according to other information doctors receive, including the results of early ultrasound scans, which give additional information regarding the gestational age. A baby is estimated to be due (the due date) at 40 weeks of gestation.

At a gestational age of 40 weeks, boys who weigh more than about 9 pounds 4 ounces (4.2 kilograms) are large for gestational age (LGA). Girls who weigh more than about 9 pounds 1 ounce (4.1 kilograms) are LGA. Doctors use published growth charts or computer apps to evaluate babies at other gestational ages.

Macrosomia (large body) is a related term used to describe infants who weigh more than 9 pounds 15 ounces (4.5 kilograms).

Causes of LGA Newborn

Large newborns may be normal babies who simply are large because the parents are large. However, certain problems in the mother sometimes cause babies to be large for gestational age.

The most common cause of LGA newborns is

Other risk factors for having LGA newborns include

The reason for excessive growth of the fetus varies but primarily results from an abundance of nutrients combined with hormones in the fetus that stimulate growth. In pregnant women who have poorly controlled diabetes, a large amount of sugar (glucose) crosses the placenta (the organ that provides nourishment to the fetus), resulting in high levels of glucose in the fetus’s blood. The high levels of glucose trigger the release of increased amounts of the hormone insulin from the fetus’s pancreas. The increased amount of insulin results in accelerated growth of the fetus, including almost all organs except the brain, which grows normally.

Symptoms of LGA Newborn

Symptoms of large-for-gestational-age newborns are mainly related to any complications that occur.

Complications

Common complications in large-for-gestational-age newborns include the following:

Diagnosis of LGA Newborn

  • Before birth, measurement of the uterus and ultrasonography

  • After birth, assessment of gestational age and size and weight of the baby

During pregnancy, doctors measure the distance on the woman's abdomen from the top of the pubic bone to the top of the uterus (fundus). This measurement, called a fundal height measurement, corresponds roughly with the number of weeks of pregnancy. If the measurement is high for the number of weeks, the fetus may be larger than expected.

After birth, LGA is diagnosed by assessing the gestational age and the weight of the baby.

LGA newborns are assessed for any complications. Blood sugar is measured to detect hypoglycemia, and doctors do a thorough examination to look for birth injuries and structural or genetic abnormalities.

Prognosis of LGA Newborn

The most common problems of LGA infants (hypoglycemia, birth injuries, and lung problems) typically resolve over a few days with no long-term consequences.

As adults, LGA girls have an increased risk of having an LGA infant. All LGA infants are at risk of obesity and may have an increased risk of heart disease.

Treatment of LGA Newborn

  • Treatment of complications

There is no specific treatment for large-for-gestational-age newborns, but underlying conditions and complications are treated as needed.

Newborns with polycythemia Polycythemia in the Newborn Polycythemia is an abnormally high concentration of red blood cells. This disorder may result from postmaturity, diabetes in the mother, twin-to-twin transfusions, in which blood flows from... read more may be given intravenous fluids. If the polycythemia is severe, the doctor may remove some blood and replace it with saline (partial exchange transfusion), which dilutes the remaining red blood cells.

Newborns with hypoglycemia are treated with frequent feedings, or sometimes are given glucose with fluids by vein.

Respiratory distress and meconium aspiration are treated with supplemental oxygen or other supportive devices such as continuous positive airway pressure (CPAP—a technique allows newborns to breathe on their own while being given slightly pressurized oxygen) or a mechanical ventilator Mechanical Ventilation Mechanical ventilation is use of a machine to aid the movement of air into and out of the lungs. Some people with respiratory failure need a mechanical ventilator (a machine that helps air get... read more , depending on the severity of the problem.

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