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.
(See also Overview of General Problems in Newborns Overview of General Problems in Newborns Problems in newborns may develop Before birth while the fetus is growing During labor and delivery After birth About 9% of newborns need special care after birth due to prematurity, problems... read more .)
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 Newborns
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
Having had previous LGA babies
Genetic abnormalities or syndromes (for example, Beckwith-Wiedemann syndrome or Sotos syndrome)
Excessive weight gain during pregnancy (the fetus gets more calories as the mother gains more weight)
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 Newborns
Symptoms of large-for-gestational-age (LGA) newborns are mainly related to any complications that occur.
Common complications in LGA newborns include the following:
Birth injuries Birth Injuries in Newborns Birth injury is damage that occurs as a result of physical pressure during the birthing process, usually during transit through the birth canal. Many newborns have minor injuries during birth... read more : Common injuries include stretching of the nerves in the shoulder (brachial plexus injuries Nerve injuries Birth injury is damage that occurs as a result of physical pressure during the birthing process, usually during transit through the birth canal. Many newborns have minor injuries during birth... read more ) and fractures.
Difficult delivery: Vaginal delivery Labor Labor is a series of rhythmic, progressive contractions of the uterus that gradually move the fetus through the lower part of the uterus (cervix) and birth canal (vagina) to the outside world... read more , especially if the fetus is in a breech presentation Breech presentation Position refers to whether the fetus is facing rearward (toward the woman’s back—that is, face down when the woman lies on her back) or forward (face up). It’s important to check the baby’s... read more , may be difficult when the fetus’s head is large in comparison with the mother’s pelvis. Cesarean delivery Cesarean Delivery Cesarean delivery is surgical delivery of a baby by incision through a woman’s abdomen and uterus. In the United States, up to 30% of deliveries are cesarean. Doctors use a cesarean delivery... read more (C-section) is commonly done for LGA infants.
Perinatal asphyxia Perinatal asphyxia Birth injury is damage that occurs as a result of physical pressure during the birthing process, usually during transit through the birth canal. Many newborns have minor injuries during birth... read more : This complication is a decrease in blood flow to the baby before, during, or just after delivery. This complication may result from a problem with the placenta before or during delivery or from difficulty delivering an LGA baby for reasons noted above.
Meconium aspiration Meconium Aspiration Syndrome Meconium aspiration syndrome is trouble breathing (respiratory distress) in a newborn who has breathed (aspirated) a dark green, sterile fecal material called meconium into the lungs before... read more : LGA babies may pass meconium (dark green fecal material that is produced in the fetus's intestine before birth) in the amniotic fluid and take forceful gasps that cause the meconium-containing amniotic fluid to be breathed (aspirated) into the lungs.
Low blood sugar (glucose) levels (hypoglycemia Hypoglycemia Hypoglycemia is abnormally low levels of sugar (glucose) in the blood. Hypoglycemia is most often caused by medications taken to control diabetes. Much less common causes of hypoglycemia include... read more ): If the fetus has been exposed to high glucose levels because the mother's diabetes was poorly controlled during pregnancy, the fetus has a high level of insulin. At the time of delivery, the placental supply of glucose is abruptly stopped, and the high level of insulin can rapidly drop the baby's blood sugar level, resulting in hypoglycemia. Hypoglycemia may cause no symptoms, but some babies are lethargic and limp and some are jittery and very excitable. Despite their large size, newborns of mothers with diabetes often do not feed well for the first few days.
Lung problems: Lung development may be delayed in newborns whose mothers have diabetes, and the babies are at increased risk of respiratory distress syndrome Respiratory Distress Syndrome in Newborns Respiratory distress syndrome is a lung disorder in premature newborns in which the air sacs in their lungs do not remain open because a substance that coats the air sacs called surfactant is... read more or transient tachypnea of the newborn Transient Tachypnea of the Newborn Transient tachypnea of the newborn is temporary difficulty with breathing and often low blood oxygen levels due to excessive fluid in the lungs after birth. This disorder can occur in premature... read more , even when they are not preterm.
Birth defects Overview of Birth Defects Birth defects, also called congenital anomalies, are physical abnormalities that occur before a baby is born. They are usually obvious within the first year of life. The cause of many birth... read more : Infants of mothers with poorly controlled diabetes have an increased risk of birth defects, including ones that involve the brain Overview of Brain and Spinal Cord Birth Defects Birth defects of the brain and spinal cord can occur in early or late fetal development. Typical symptoms include intellectual disability, paralysis, incontinence, or loss of sensation in some... read more , heart Overview of Heart Defects About one in 100 babies is born with a heart defect. Some are severe, but many are not. Defects may involve abnormal formation of the heart's walls or valves or of the blood vessels that enter... read more , kidneys Kidney Defects There are several different birth defects that affect the kidneys (the two organs that filter waste from the blood to make urine). These defects are not usually apparent at the doctor's examination... read more , digestive tract Overview of Digestive Tract Birth Defects The digestive organs may be incompletely developed or abnormally positioned, causing blockages, or the muscles or nerves of the digestive tract may be defective. Symptoms depend on the location... read more , and lower part of the spine Neural Tube Defects and Spina Bifida Neural tube defects are a certain type of birth defect of the brain, spine, and/or spinal cord. Neural tube defects can result in nerve damage, learning disabilities, paralysis, and death. The... read more .
Excess red blood cells (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 ): LGA babies may have a higher blood count than usual. Too many red blood cells may cause the blood to become too thick, which may slow blood flow. Newborns with polycythemia have a reddish complexion and are sluggish. Polycythemia can contribute to hypoglycemia, respiratory distress, and hyperbilirubinemia.
Diagnosis of LGA Newborns
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.
Ultrasonography Ultrasonography Prenatal diagnostic testing involves testing the fetus before birth (prenatally) to determine whether the fetus has certain abnormalities, including certain hereditary or spontaneous genetic... read more can be used to assess the size of the fetus and estimate fetal weight to confirm the large-for-gestational-age (LGA) diagnosis.
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 for LGA Newborns
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 Newborns
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 early (within 1 hour after birth) and 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.