average baby weight
A newborn baby weighing 9-pounds is considered large and is medically known as fetal macrosomia.

Yes, a nine-pound baby is big. The condition is medically known as fetal macrosomia or large for gestational age (LGA). It includes all newborn babies who weigh more than the average baby weight for the number of weeks of pregnancy.

According to the U.S. statistics from 1991, babies could be called LGA or as babies with fetal macrosomia if they weigh more than 8.13 pounds at birth. The risk of complications increases if the baby weighs 9.11 pounds.

What causes babies to be born big?

Newborn babies in the United States are born with a higher weight with the passing years. 

Certain babies are born big due to one or more of the following causes:

  • Genetic factors. Problems in the genes of the baby can cause the baby to be born big.
  • Size of the parents. If the parents of the baby are large, their baby is likely to be big. Big babies can get macrosomia from one of their parents.
  • Weight gain during pregnancy. If the baby’s mother gains a lot of weight during the pregnancy, the baby is likely to suffer from macrosomia.
  • Maternal conditions such as obesity and diabetes. If the baby’s mother had diabetes before the pregnancy or has developed diabetes during the pregnancy, their baby is most likely to have larger shoulders and higher body fat compared to those whose mothers do not have diabetes. Babies born to overweight or obese mothers tend to have fetal macrosomia.
  • A history of fetal macrosomia. If the mother has given birth to a big baby in any of their previous pregnancies, they are more likely to give birth to another big baby in their next pregnancy.
  • Maternal age. Women older than 35 years tend to have big babies.

How is macrosomia diagnosed?

Before the baby’s birth, the term fetal macrosomia is used instead of large for gestational age (LGA).

Macrosomia can be diagnosed even before a baby is born by looking at the size of the pregnant abdomen.

The doctor may order an ultrasound to make sure if the unborn baby is big.

How is macrosomia managed?

The doctor may plan an early delivery, preferably via a cesarean delivery if they find out through prenatal examinations that the baby is big.

After delivery, the blood sugar levels of the baby will be observed for 12 hours to check for low blood sugar levels. The baby will be examined for any injuries or developmental anomalies as well.

What are the possible complications of macrosomia?

A big baby may cause problems during delivery, including delivery taking a long labor time, and difficulty in giving birth. The baby may develop injury in the shoulder (broken collar bone).

Complications in the mother due to macrosomia include:

  • Injury to the birth canal
  • Increased bleeding after delivery
  • Uterine rupture

If the mother suffers from diabetes and their baby is born big, the big baby can face complications, such as:

  • Hypoglycemia (low blood sugar) in the first 12 hours after birth. The baby may require intensive care and may be shifted to an intensive care unit
  • Breathing trouble (respiratory distress syndrome)
  • Birth defects
  • Jaundice (big babies are more likely to have more red blood cells, a condition called polycythemia, which can result in their greater breakdown in the liver, leading to excess bilirubin in the blood, and manifesting as jaundice, which is a yellowish discoloration of the eyes, skin, and nails)

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Medically Reviewed on 11/2/2021
References
Image Source: shaunl / Getty Images

Patel EA. Macrosomia. Medscape. https://emedicine.medscape.com/article/262679-overview

Mayo Clinic. Fetal macrosomia. https://www.mayoclinic.org/diseases-conditions/fetal-macrosomia/symptoms-causes/syc-20372579