Help! My Baby Is Too Big!
The ultrasound tech pressed the wand firmly against my belly as a look of surprise came over her face.
“Wow!” she exclaimed. “That's a big baby!”
Pregnant with my fourth child, I was no stranger to hearing that my babies were “big.” My son had weighed in at over 9 pounds at birth, and this baby, a girl, was estimated to be close to 11 pounds at full term.
But what exactly does the diagnosis of having a “big” baby mean? If you have this experience, should you be concerned? Will the care for you and your baby be different?
What is a “big” baby?
Your care provider uses a set of criteria to determine if your baby is “large for gestational age,” which could mean a variety of things. By definition, macrosomia, the official term for a big baby, is a weight of more than 8 pounds and 13 ounces. If your belly is measuring ahead of what would normally be expected, for instance, you may need an ultrasound to determine fetal size, or your regular ultrasound may reveal that your baby is larger than the criteria for average fetal development.
The difficulty in diagnosing macrosomia is that ultrasounds can be off by as much as two pounds, so even if your baby is measuring as large, the real weight could be much different. “Estimating the weight of the baby (fetus) is an inexact science,” says James A. O’Brien, M.D., FACOG, Medical Director of Inpatient Obstetrics at Women and Infants’ Hospital of Rhode Island. He explains that in one study that examined the efficacy of ultrasound-estimated weight, the weight prediction was only within 10% of the actual birth weight 80% of the time.
What causes a “big” baby?
There can be many causes of having a larger-than-average baby. Advanced or very young maternal age, weight gain, having multiple children, or gestational diabetes are common causes for bigger babies. Polyhydramnios is also associated with bigger babies.
Will you need a c-section?
According to the American College of Obstetricians and Gynecologists (ACOG), the answer is “not necessarily.” “Suspecting that a baby is macrosomic (large) is not an indication to induce or deliver by cesarean before 39 weeks,” they state. However, they do recommend advising patients to consider cesarean delivery for fetal weights above 9 pounds and 15 ounces for diabetic women and 11 pounds for non-diabetic women, says Dr. O'Brien. “These recommendations are made in an effort to avoid both maternal and newborn birth injury,” he explains.
Will the baby get stuck?
One of the biggest concerns with having a so-called “big” baby is the risk for shoulder dystocia—a condition when the baby's shoulder gets wedged against the woman's pelvis, making vaginal delivery almost impossible and increasing the risk for oxygen deprivation and other complications such as hemorrhaging for the mother. However, studies have shown that it's almost impossible to associate shoulder dystocia with macrosomia because 1) the diagnosis is often wrong and 2) even small babies can have shoulder dystocia.
The truth is, baby size doesn't necessarily mean a harder delivery, nor can a mother's size vs. baby's size predict how well labor will go. A successful vaginal delivery depends more on the size of the mother's pelvic inlet (the inside opening of the pelvis) and how the baby is positioned during its descent through the birth canal. I have actually seen a full-term woman at barely over 100 pounds deliver a 9-pound baby, so appearances can be deceiving.
The bottom line: If you are told that your baby is big, don't panic. Follow your care provider's recommendations for healthy eating and exercise, understand that estimating true fetal weight is usually very tricky, and don't have an induction or c-section unless it is truly medically necessary.
How much did your baby weigh?