Fetal Macrosomia

During pregnancy, physicians must carefully monitor both infant and mother to ensure that the pregnancy is developing normally and to diagnose and treat any issues that can result in potential birth injuries. One possible complication is fetal macrosomia, a condition in which babies are unusually large for their gestational age. Macrosomia can lead to a host of medical issues, including birth injuries and life-threatening medical complications.

Fetal Macrosomia Defined

When an infant’s estimated weight is higher than 90% of the average weight of babies in the same age range, they are considered large for their gestational age, yet that’s only part of how fetal macrosomia is defined. Macrosomia is also considered a high-risk pregnancy in which the mother and infant are at risk for medical problems.

Most doctors consider macrosomia to be a birth weight of more than 9 pounds, 15 ounces, while others consider it to be a birth weight of more than 8 pounds, 13 ounces.

According to the American Academy of Pediatrics (AAP), a little over 10% of all pregnancies in the United States result in macrosomia. It makes normal delivery extremely difficult, often ending in a cesarean section surgery (C-section)  and/or early labor induction.

Fetal Macrosomia Symptoms

Unfortunately, fetal macrosomia is often difficult to detect during pregnancy, but there a few tests that can be performed that indicate if there are symptoms and signs of an unusually large baby, including:

  • Excessive Abdominal Fluid: During a prenatal visit, a physician can measure amniotic fluid via an ultrasound. Excessive amounts of amniotic fluid may indicate that the infant is larger than the expected size. Larger babies tend to urinate more, which leads to a higher amount of amniotic fluid.
  • Fundal Height: During a prenatal visit, physicians can also measure the distance of a pregant woman’s pelvic bone to her uterus. Known as a fundal height measurement, this gives doctors a better understanding of how large the infant is.

Fetal Macrosomia Causes

According to Carol L. Archie, M.D.  of the University of California at Los Angeles School of Medicine, maternal diabetes and obesity can lead to macrosomia as an infant typically receives too many nutrients.

“Big parents often have big babies, but sometimes babies are unusually large because the mother is obese or has developed gestational diabetes during her pregnancy that was undiagnosed or untreated,” Dr. Archie says.

Other factors that have been associated fetal macrosomia include post-term pregnancies, mothers of hispanic origin, a history of previous large infants. Male infants also have a higher rate of being born with macrosomia when compared to female infants.  In addition, women over the age of 35 have a higher risk of having large babies.

In some cases, there is no known cause of fetal macrosomia.

Fetal Macrosomia Complications

Both mother and infant are at risk for complications. For mothers, one of the major complications include a difficult pregnancy. If a normal labor and delivery occurs, a large infant may become caught in the birth canal, resulting in doctors using birth-assisting tools to help delivery. This may cause genital tract lacerations, excessive bleeding, and the need for an emergency C-section.

Infants are at heightened risk for birth injuries. For instance, a difficult labor and delivery process puts a baby in danger of shoulder dystocia, nerve damage, and oxygen deprivation, which can lead to permanent health issues and disorders. Furthermore, infants with a high birth weight may have obesity problems during childhood and are at risk of developing metabolic syndrome, a condition marked by high blood sugar levels, increased blood pressure, and excessive body fat around the waist and abdominal area. When these issues are combined, the infant is also in danger of heart disease and stroke later on in life.

Fetal Macrosomia Treatment Options

If fetal macrosomia is caused by gestational diabetes, physicians will work closely to ensure the mother keeps her blood sugar regulated. This can include following a healthy diet plan and a safe exercise regime.

Although having a normal delivery is necessarily impossible for mothers with large infants, a C-section, in many cases, has been the best treatment. Although a C-section comes with its own set of risks and complications, the benefits typically outweigh the hazards. For example, a C-section will eliminate the possibility of birth injuries caused by birth-assisting tools as well as injuries such as shoulder dystocia and a fractured collarbone.

Fetal Macrosomia Prevention Tips

Even though there are some cases in which fetal macrosomia occurs for no apparent reason, pregnant women can help reduce the chances by:

  • Watching Weight Gain: Although this may be difficult during pregnancy, gaining between 25 to 35 pounds only, the ideal weight gain during pregnancy, is recommended by most doctors. It’s important to note, however, that this is just a general guideline, and doesn’t apply to each individual case. A physician should work closely with you in order to find the ideal weight gain amount for your situation.
  • Control Diabetes: Controlling blood sugar during pregnancy is one of the best ways to help prevent fetal macrosomia.
  • Keep All Prenatal Appointments: Prenatal check-ups are crucial during pregnancy as it allows doctors to examine the pregnancy and run tests to ensure everything is normal. It also helps them prepare for your upcoming birth and the steps needed should you show signs of carrying a large infant.