Fetal Macrosomia: Babies Born Overweight

The importance of babies' birth weight doesn't come down to mere aesthetic issues. Their health can be affected by certain weight-related conditions, so it's recommended to perform the necessary check-ups and prevent difficulties during and after delivery.
Fetal Macrosomia: Babies Born Overweight

Last update: 29 December, 2018

At the time of birth, doctors evaluate many characteristics of newborns to determine their state of health. These include their size, complexion and weight. In this last aspect, babies born overweight make up a group that requires specific care.

The parameter considered normal for newborn babies is a weight of approximately 7.7 pounds. In girls, this decreases to about 7.3 pounds. When babies are born weighing less than 5.5 pounds, they’re considered underweight.

On the other hand, when they’re born weighing more than 9.9 pounds, babies are overweight. This is also known as fetal macrosomia.

Factors to consider

How much a baby weighs at birth depends on many factors, including:

  • Age, weight and nutritional status of the mother, as well as her lifestyle
  • Duration of pregnancy and possible complications that occurred during it
  • Number of previous pregnancies and amount of time between them
  • The mother’s emotional stability. Remember that all stress affects the growth of the fetus.

What can cause fetal macrosomia?

Fetal macrosomia, which is characterized by considerable growth of the fetus before birth, can be caused by several factors. The first of these is when the mother has diabetes.

According to experts, the reasons why children of diabetic mothers have certain alterations haven’t been identified. But one such alteration includes deregulation in the growth of the fetus.

In addition, fetal macrosomia can also be caused if the mother is overweight. The same condition is replicated in the fetus. Also, the prolongation of pregnancy beyond week 40 can also trigger the baby to weigh more than 9 pounds.

Genetic predisposition should also not be ignored: if the mother or father is of large size, it’s likely that they’ll transmit genes for a similar growth pattern.

Fetal Macrosomia: Babies Born Overweight

Risk for babies born overweight

The first thing that needs to be clarified is that babies born overweight don’t necessarily suffer from a health problem. They can be perfectly normal children with only a difference in size. 

However, we must also mention that this circumstance may lead to the appearance of certain conditions. Some of the risks of babies born overweight include:

Obstetric trauma

Due to their considerable size, the delivery of babies born overweight is usually more complex than that of smaller babies. Shoulder dystocia represents one of the most common problems.

Shoulder dystocia occurs when the child’s shoulder remains stuck in the mother’s pelvis after the head has already emerged. This may have to be remedied with a clavicle fracture.

For the mother, meanwhile, the risks that this entails include inconveniences such as tears in the birth canal or hemorrhaging. Many of these pregnancies result in a cesarean in order to avoid complications that can have fatal outcomes in less developed countries.

“The parameter considered normal for newborn babies is an approximate weight of 7.7 pounds.”


Especially in babies whose mothers suffered from gestational diabetes, hypoglycemia is a possible result. Basically, it consists of a decrease in sugar levels in the newborn caused by too much insulin.

The fetus secretes this hormone during pregnancy to synthesize the high levels of sugar that the mother transferred to the fetus. Once the baby is born, the contribution of sugar ceases, but not the insulin index in the baby’s body.

Other complications

In addition to the two complications mentioned above, we can add the following possible disadvantages for babies born overweight:

  • Respiratory distress: certain hormonal and metabolic dis-regulations of the fetus can cause delayed maturation of the lungs.
  • Polycythemia: the presence of too many red blood cells in the blood. The blood becomes more viscous and there may be some decrease in the performance of the central nervous system.
  • Hyperbilirubinemia: The level of bilirubin, elevated by the destruction of red blood cells in the blood vessels, can cause neuronal alterations.
Fetal Macrosomia: Babies Born Overweight

On the other hand, miscarriages may occur more often with macrosomic babies. The mother’s diabetes can damage the placenta, making it unable to transfer necessary nutrients to the fetus for its development.

Finally, compression of the umbilical cord may also be present. Although the fetus and uterus grow simultaneously, sometimes the size of the fetus continues to increase without the uterus enlarging. Thus, the umbilical cord would be pressed and the fetus’ life would be in danger.

These reasons only confirm the importance of regular check-ups during pregnancy, especially if you know you’re carrying a baby with macrosomia. Early diagnosis and follow-up are irreplaceable prevention mechanisms.


This text is provided for informational purposes only and does not replace consultation with a professional. If in doubt, consult your specialist.