Fetal Macrosomia

What is Fetal Macrosomia?

Fetal macrosomia is a term that refers to a child that is born at a significantly larger size than the average newborn. Specifically, if a child is born over eight pounds, thirteen ounces or over 4,000 grams, the child is said to have fetal macrosomia. A diagnosis of fetal macrosomia is not dependent upon a child’s gestational age and is determined only by birth weight.

This condition can cause a number of issues and complications, both for the mother and the child. During labor, the mother may have difficulty with a natural childbirth and could experience tearing, uterine rupture, and excessive bleeding postpartum. They may also need to have an emergency cesarean if they are unable to give birth naturally due to the baby’s size. Children born with fetal macrosomia are more prone to develop childhood diabetes, and problems with blood sugar and metabolism.

There are numerous potential contributing factors to fetal macrosomia. Some of these include gestational diabetes and maternal obesity. A longer than normal gestation (i.e. a pregnancy that lasts longer than 40 weeks) and a history of giving birth to babies over eight pounds, thirteen ounces are also possible contributing factors.

What are the Symptoms of Fetal Macrosomia?

Oftentimes, it is difficult to determine is a child is going to be macrosomic before they are born and weighed.

Symptoms include

If a woman has more amniotic fluid than normal, this can be a sign of fetal macrosomia. Doctors often also measure a woman’s fundal height which is the distance from a woman’s pubic bone to the top of the uterus. A high fundal height could also be an indication. The problem is, though, that a woman could have one or both of these issues and still give birth to a baby of “normal” weight.

Children born with fetal macrosomia may suffer from injuries during birth including shoulder dystocia, or a brachial plexus injury. They also may be born with extremely low blood sugar or blood disorders.

Fetal Macrosomia Causes

There are three known risk factors for fetal macrosomia. The first one is being diabetic or getting gestational diabetes during pregnancy. In as many as fifty percent of women with diabetes during pregnancy, the fetus ends up with fetal macrosomia. There is also a difference in how the extra weight distributes; there’s a greater amount of body fat, thicker upper-extremity skinfold measurements and a smaller head to the abdominal circumference. Women who are obese before pregnancy have a higher likelihood of the fetus having fetal macrosomia; in addition to prior weight, how much weight gain during pregnancy affects the risk of fetal macrosomia. Women who had one child with fetal macrosomia are more likely to have fetal macrosomia in pregnancies afterward. The sex of the child and volume of amniotic fluid can also influence the birth weight of a fetus. A male child weighs more than a female child, increasing the risk of fetal macrosomia.

How is a Fetal Macrosomia Treated?

If fetal macrosomia is indicated prior to giving birth, doctors will closely monitor the health of the fetus and mother and may recommend a cesarean delivery rather than a natural one if the fetus is suspected to be especially large or the mother has been diagnosed with gestational diabetes or preeclampsia. Once a child with fetal macrosomia is born, they will be examined and tested for injuries or health issues and treated accordingly.

Fetal Macrosomia Prevention

The best prevention for fetal macrosomia is to be healthy and live a healthy lifestyle. If you’re overweight before getting pregnant, look into losing weight and managing your weight gain during pregnancy. The recommended weight gain is twenty-five to thirty-five pounds to support the fetus’s growth and development without excessive growth. If you have diabetes or gestational diabetes, work with your healthcare provider to keep diabetes under control; the best way to prevent fetal macrosomia is to control your blood sugar levels. Including regular physical activity into your lifestyle, such as working out or even a daily walk, helps to keep your weight under control and helps manage diabetes if you have it. Being healthy and taking care of yourself before and during pregnancy will make the pregnancy that much easier, and it’ll help prevent fetal macrosomia.

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Last Reviewed:
September 21, 2016
Last Updated:
December 21, 2017