Fetal Macrosomia

1 What is Fetal Macrosomia?

Fetal macrosomia is a condition in which a baby is born weighing more than 8 pounds, 1 ounces (4,000 grams). It is diagnosed in approximately 9 percent of newborns per year.

Fetal macrosomia can complicate vaginal delivery and can put the baby at an increased risk of injury during birth which can lead to health problems in the future.

2 Symptoms

Possible signs and symptoms of fetal macrosomia include:

  • large fundal height, which is an increase in the height from the distance on from the top of the uterus to the pubic bone.  
  • presence of excessive amniotic fluid (polyhydramnios). The amniotic fluid is a fluid that surrounds and protects the fetus during pregnancy. The total amount of amniotic fluid reflects the urine output of a baby, thus a large baby will produce more urine.

Fetal macrosomia is difficult to diagnose during pregnancy. 

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3 Causes

The exact cause of fetal macrosomia remains unknown in most cases.

Some cases are believed to be as a result of genetic factors, maternal conditions like Diabetes mellitus or obesity and even by medical conditions that cause the fetus to grow faster.

4 Making a Diagnosis

Fetal macrosomia is difficult to diagnose during pregnancy.

A definitive estimation of the baby's body weight can only be made when the baby is born. It is important to keep in mind that assessment of a baby's size should correspond with the gestational age.

Tests that can be used to diagnose fetal macrosomia include ultrasonography and antenatal testing. Antenatal tests like non-stress testing and fetal biophysical testing can be used to detect the baby's overall well-being.

A non-stress test is used to check the baby's heart rate in response to his or her movements.

A biophysical test combines non-stress testing and ultrasound to monitor the baby's movement, tone, breathing and volume of amniotic fluid.

5 Treatment

In most cases, no treatment is needed for a baby with fetal macrosomia.

Fetal macrosomia may not be prevented. However, maintaining a healthy lifestyle especially during pregnancy can be helpful.

6 Prevention

Fetal macrosomia may not be prevented. 

Vaginal delivery can still be used when fetal macrosomia is diagnosed but the woman will need to give birth in a hospital just in case forceps are needed.

A C-section is usually recommended in cases where the woman has diabetes or the baby weighs more than 11 pounds (5,000 grams). A C-section can also be performed if the baby's shoulders get stuck behind the pelvic bone (shoulder dystonia).

After birth, it is necessary to check if there are any signs of birth injuries, hypoglycemia (abnormally low levels of blood sugar) and polycythemia.

7 Lifestyle and Coping

Lifestyle modifications are necessary in order to cope with fetal macrosomia.

If fetal macrosomia is diagnosed, it is important for the woman to keep calm since stress can affect the health of both the fetus and mother.

8 Risks and Complications

Some of the factors that increase the risk of fetal macrosomia include:

  • Maternal diabetes whether it develops before pregnancy (pregestational) or develops during pregnancy (gestational)
  • A history of fetal macrosomia
  • Maternal obesity
  • Excessive weight gain during pregnancy
  • Previous pregnancies since the risk of fetal macrosomia develops with each pregnancy
  • Having a boy
  • Overdue pregnancy (pregnancy that lasts more than two weeks past the due date)
  • Being older than 35

Complications of fetal macrosomia can be divided into maternal and newborn and childhood risks.

Maternal risks include:

  • Labor problems in which a C-section might be required
  • Genital tract lacerations such as tearing of the vaginal tissues and muscles between the vagina and anus
  • Bleeding after giving birth and rupture of the uterus. 

Newborn and childhood risks include:

Metabolic syndromes include high blood pressure, high blood sugar levels, and abnormal cholesterol levels that can increase the risk of developing heart disease, stroke and diabetes.

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