Fetal macrosomia



What is fetal macrosomia?

The term “fetal macrosomia” is 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 (4,500 grams).

Fetal macrosomia may complicate vaginal delivery and could put the baby at risk of injury during birth. Fetal macrosomia also puts the baby at increased risk of health problems after birth.

How common is fetal macrosomia?

This fetal macrosomia is extremely common. It commonly affects more females than males. It can affect patients at any age. It can be managed by reducing your risk factors. Please discuss with your doctor for further information.


What are the symptoms of fetal macrosomia?

The common symptoms of fetal macrosomia are:

  • 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.

There may be some symptoms not listed above. If you have any concerns about a symptom, please consult your doctor.

When should I see my doctor?

If you have any signs or symptoms listed above or have any questions, please consult with your doctor. Everyone’s body acts differently. It is always best to discuss with your doctor what is best for your situation.


What causes fetal macrosomia?

Fetal macrosomia can be caused by genetic factors as well as maternal conditions, such as obesity or diabetes. Rarely, a baby might have a medical condition that speeds fetal growth.

In some cases, what causes a larger than average birth weight remains unexplained.

Risk factors

What increases my risk for fetal macrosomia?

There are many risk factors for fetal macrosomia, such as:

  • Maternal diabetes. If you had diabetes before pregnancy (pre-gestational diabetes) or you develop diabetes during pregnancy (gestational diabetes), fetal macrosomia is more likely. If your diabetes is poorly controlled, your baby is likely to have larger shoulders and greater amounts of body fat than would a baby whose mother doesn’t have diabetes.
  • A history of fetal macrosomia. If you’ve previously given birth to a baby diagnosed with fetal macrosomia, you’re at increased risk of having another baby who has the condition. Also, if you weighed more than 8 pounds, 13 ounces at birth, you’re more likely to have a large baby.
  • Maternal obesity. Fetal macrosomia is more likely if you’re obese.
  • Excessive weight gain during pregnancy. Gaining too much weight during pregnancy increases the risk of fetal macrosomia.
  • Previous pregnancies. The risk of fetal macrosomia increases with each pregnancy. Up to the fifth pregnancy, the average birth weight for each successive pregnancy typically increases by up to about 4 ounces (113 grams).
  • You’re having a boy. Male infants typically weigh slightly more than female infants. Most babies who weigh more than 9 pounds, 15 ounces (4,500 grams) are male.
  • Overdue pregnancy. If your pregnancy continues by more than two weeks past your due date, your baby is at increased risk of fetal macrosomia.
  • Maternal age. Women older than 35 are more likely to have a baby diagnosed with fetal macrosomia.

Fetal macrosomia is more likely to be a result of maternal diabetes, obesity or weight gain during pregnancy than other causes. If these risk factors aren’t present and fetal macrosomia is suspected, it’s possible that your baby might have a rare medical condition that affects fetal growth.

Your health care provider might recommend prenatal diagnostic tests and perhaps a visit with a genetic counselor, depending on the test results.

Diagnosis & treatment

The information provided is not a substitute for any medical advice. ALWAYS consult with your doctor for more information.

How is fetal macrosomia diagnosed?

It can be difficult to get a sense of your baby’s exact weight while in utero, but there are ways you and your practitioner can get some indication of your baby’s size. First, your practitioner will check your fundal height — the distance between the top of your growing uterus and your pubic bone — for clues (a higher than expected height may mean a larger baby). Your practitioner will also manually feel your abdomen to get a sense of fetus size (this may be slightly uncomfortable for you — but rest assured, it doesn’t hurt the baby). Another way to get an idea of your baby’s weight is through your routine ultrasound scans, which will give rough measurements of your baby’s weight and the level of amniotic fluid. Why measure amniotic fluid to get info on a baby’s size? Excessive amniotic fluid — a condition known as polyhydramnios — is often associated with macrosomia (since larger babies pee out larger quantities of urine and more urine means more amniotic fluid). These measurements plus your medical history can give a strong indication of whether your baby is at risk for macrosomia, though a definite diagnosis won’t be made until your baby’s weight is confirmed at birth.

How is fetal macrosomia treated?

If your health care provider suspects fetal macrosomia, a vaginal delivery isn’t necessarily out of the question. However, you’ll need to give birth in a hospital — in case forceps or a vacuum device are needed during delivery or a C-section becomes necessary.

Inducing labor — stimulating uterine contractions before labor begins on its own — isn’t generally recommended. Research suggests that labor induction doesn’t reduce the risk of complications related to fetal macrosomia and might increase the need for a C-section.

Your health care provider might recommend a C-section if:

  • You have diabetes. If you had diabetes before pregnancy or you develop gestational diabetes and your health care provider estimates that your baby weighs 9 pounds, 15 ounces (4,500 grams) or more, a C-section might be the safest way to deliver your baby.
  • Your baby weighs 11 pounds or more and you don’t have a history of maternal diabetes. If you don’t have pre-gestational or gestational diabetes and your health care provider estimates that your baby weighs 11 pounds (5,000 grams) or more, a C-section might be recommended.
  • You delivered a baby whose shoulder got stuck behind your pelvic bone (shoulder dystocia). If you’ve delivered one baby with shoulder dystocia, you’re at increased risk of the problem occurring again. A C-section might be recommended to avoid the risks associated with shoulder dystocia, such as a fractured collarbone.

If your health care provider recommends an elective C-section, be sure to discuss the risks and benefits.

After your baby is born, he or she will likely be examined for signs of birth injuries, abnormally low blood sugar (hypoglycemia) and a blood disorder that affects the red blood cell count (polycythemia). He or she might need special care in the hospital’s neonatal intensive care unit.

Keep in mind that your baby might be at risk of childhood obesity and insulin resistance and should be monitored for these conditions during future checkups.

Also, if you haven’t previously been diagnosed with diabetes, after childbirth your health care provider will test you for the condition. During future pregnancies, you’ll be closely monitored for signs and symptoms of gestational diabetes — a type of diabetes that develops during pregnancy.

Lifestyle changes & home remedies

What are some lifestyle changes or home remedies that can help me manage fetal macrosomia?

The following lifestyles and home remedies might help you cope with fetal macrosomia:

  • If your health care provider suspects fetal macrosomia during your pregnancy, you might feel anxious about childbirth and your baby’s health — and worrying can make it hard to take care of yourself.
  • Consult your health care provider about what you can do to relieve stress and promote your baby’s health. Also consider seeking information and support from women who’ve had babies diagnosed with fetal macrosomia.

If you have any questions, please consult with your doctor to better understand the best solution for you.

Hello Health Group does not provide medical advice, diagnosis or treatment.

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Review Date: September 8, 2017 | Last Modified: September 8, 2017