Fetal macrosomia

Fetal macrosomia is a term used to describe a newborn who's significantly larger than average.

A baby diagnosed with fetal macrosomia has a birth weight of more than 8 pounds, 13 ounces (4,000 grams), regardless of his or her gestational age. About 9 percent of babies born worldwide weigh more than 8 pounds, 13 ounces. However, the risks associated with fetal macrosomia increase greatly when birth weight is more than 9 pounds 15 ounces (4500 grams).

Fetal macrosomia makes vaginal delivery difficult and puts the baby at risk of injury during birth. Fetal macrosomia also puts the baby at increased risk of health problems after birth.

Symptoms Causes Risk factors Complications Prevention

Fetal macrosomia is difficult to detect and diagnose during pregnancy. Possible signs and symptoms include:

  • Large fundal height. During prenatal visits, your health care provider might measure your fundal height — the distance from the top of your uterus to your pubic bone. A fundal height that measures larger than expected could be a sign of fetal macrosomia.
  • Excessive amniotic fluid (polyhydramnios). Too much amniotic fluid — the fluid that surrounds and protects a baby during pregnancy — might be a sign that your baby is larger than average. The amount of amniotic fluid reflects your baby's urine output, and a larger baby produces more urine. Some conditions that increase a baby's size might also increase his or her urine output.

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