Around nine percent of babies worldwide are born weighing over 8 pounds, 13 ounces and the women who deliver them are true superheroes (you go!), but when it comes to fetal macrosomia or excessive birth weight, doctors are generally vigilant.
Macro what?
Macrosomia is a Greek word that means “big body.” It is the medical term for babies born weighing 8 pounds, 13 ounces or more.
Before the baby is born, doctors can not diagnose macrosomia, and they will usually say that the baby is “big or advanced for their gestational age". What limits diagnosis is the fact that ultrasound-derived weight estimates are accurate only about 40 percent of the time [2].
What are the risks if the baby is larger than average?
For starters, a large baby may have a more complicated birth. They may have trouble passing through the birth canal, and in consequence, the mother may experience more tears and bleeding. The baby has a higher risk of suffering a fracture of the shoulder or clavicle, as well as spinal injuries. Roughly one in ten C-sections are due to the size of the baby [2].
Less commonly, a baby’s large size may point to one of a few rare diseases that cause faster growth in utero. It can also be an indicator of undiagnosed gestational diabetes in the mother, meaning she may have unknown health risks, and the baby’s blood glucose level may drop dangerously after birth [1].
Does my diet affect my baby’s size?
In general, diet does have an impact on the baby’s growth. A balanced diet and regular exercise throughout pregnancy can reduce the risk of macrosomia by almost 40 percent. Something to note is that, in this case, exercise is more important than diet; mamas who exercised regularly without changing their diets had a lower risk of having a large baby than those who controlled their diets but didn’t exercise [2].
What are some of the risk factors for macrosomia?
Maternal BMI of 30 or above.
Pregnancy weight gain of more than 26 pounds.
Gestational diabetes. [1]
Some studies show that insulin therapy works well for women with gestational diabetes whose baby shows faster growth between weeks 29 and 33 [2].
However, other factors are out of anyone's control. For example, baby boys are more likely to present macrosomia than girls and tall parents (over 5’10”) tend to have larger babies. Also, the risk of delivering a large baby increases every day after the 39th week of pregnancy [2].
Do I need to schedule a C-section if we suspect my baby has macrosomia?
This is one of the most controversial issues in obstetrics. Doctors have differing opinions, and we don’t have enough data to support a definitive answer.
On the one hand, a C-section reduces the risk of injury during childbirth for both mother and baby. However, a C-section comes with its drawbacks. The American College of Obstetricians and Gynecologists (ACOG) recommends a C-section if the baby is likely to weigh closer to 11lb. In cases of gestational diabetes, a C-section is likely to be planned if the baby’s expected birth weight is over nine pounds [2].
