Definition

Macrosomia is a condition in which a baby is abnormally large before birth. The average birth weight for babies is about 7 pounds. Babies with macrosomia have a birth weight of at least 8 pounds, 13 ounces or more.

Macrosomia occurs in more than 10% of all pregnancies in the United States. It may lead to pregnancy complications such as a greater risk of cesarean delivery, damage to the birth canal, and injury to the baby during a vaginal delivery.

Babies born with macrosomia are more likely to have low blood sugar, respiratory distress, and jaundice.

Causes

The most common cause of macrosomia is diabetes in the mother during pregnancy.

Risk Factors

Factors that may increase your chance of giving birth to a baby with macrosomia include:

• Mother having diabetes
• Mother having gestational diabetes
• Mother is obese
• Mother and/or father of large size
• Excessive weight gain by the mother during pregnancy

Signs and Symptoms

The main symptom of macrosomia is a birthweight of at least 8 pounds, 13 ounces or more. This birthweight may be estimated during prenatal testing.

Diagnosis

Your doctor will ask about your symptoms and medical history. A physical and pelvic examination will be done. An ultrasound can help determine the size of the baby before birth.

Your doctor will estimate the birth weight and evaluate any dangers for the mother and/or baby.

If the fetal macrosomia may cause potential harm during a vaginal delivery, a Cesarean delivery may be scheduled.

Treatment

Talk with your doctor about the best treatment plan for you. Treatment options include:

Feeding babies with macrosomia soon after birth is important to prevent low blood sugar in the baby.

Prevention

To help prevent macrosomia:

• Maintain a healthy weight throughout pregnancy
• Exercise as advised by your doctor
• Control blood sugar if you have diabetes
• Receive prenatal care to diagnose problems early and prevent complications

Centers for Disease Control and Prevention http://www.cdc.gov

The Society of Obstetricians and Gynaecologists of Canada http://www.sogc.org

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Zamorski MA, Biggs WS. Management of suspected fetal macrosomia. Am Fam Physician. 2001;15;63(2):302–307.

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