Dr. Says My Baby Is Too Big- What's The Deal?

Big Babies- Whats The Big Deal??

I hear this situation happen all of the time… “I went to my doctor today and they said my baby is growing 2 weeks ahead- The Doc thinks that baby will be at least 9lbs and thinks I should be induced before the baby is too big for me to push out, or a cesarean section should be scheduled.” My clients always call me right after this happens and ask something along these lines: “Leah, what’s the deal? Is this legitimate? What are the real risks? Could my pelvis really be too small?”

Most of the women whose care providers talked about induction for big baby ended up being medically induced (67%), and the rest tried to self-induce labor with natural methods (37%). Nearly one in five women said they were not offered a choice when it came to induction—in other words, they were told that they must be induced for their suspected big baby. 

When care providers brought up planning a C-section for a suspected big baby, one in three women ended up having a planned Cesarean. Two out of five women said that the discussion was framed as if there were no other options—that they must have a Cesarean for their suspected big baby.

In the end, care provider concerns about a suspected big baby were the fourth most common reason for an induction (16% of all inductions), and the fifth most common reason for a C-section (9% of all C-sections). More than half of all mothers (57%) believed that an induction is medically necessary if a care provider suspects a big baby. 

So in the U.S., most women have an ultrasound at the end of pregnancy to estimate the baby’s size, and if the baby appears large, their care provider will usually recommend either an induction or an elective C-section. Is this approach evidence-based?

This approach is based on five major assumptions:

  1. Big babies are at higher risk for shoulders getting stuck (also known as shoulder dystocia).

    • Reality: While it is true that 7-15% of big babies have difficulty with the birth of their shoulders, most of these cases are handled by the care provider without any harmful consequences for the baby. Permanent nerve injuries due to stuck shoulders are less common: they happen in 1 out of every 555 babies who weigh between 8 lbs., 13 oz. and 9 lbs., 15 oz., and 1 out of every 175 babies who weigh 9 lbs., 15 oz. or greater.

  2. Big babies are at higher risk for other birth problems. 

    • Reality: It’s possible that giving birth to a big baby can increase the risk of certain health problems for both the mother and the baby. However, the care provider’s “suspicion” of a big baby carries its own set of risks.

  3. We can accurately tell if a baby will be big.

    • Reality: Both physical exams and ultrasounds are equally bad at predicting whether a baby will be big at birth.

  4. Induction keeps the baby from getting any bigger, which lowers the risk of C-section.

    • Reality: There is conflicting evidence about whether induction for suspected big babies can improve the health of mothers and babies.

  5. Elective Cesareans for big baby are only beneficial; that is, they don’t have major risks that could outweigh the benefits

    • Reality: No researchers have ever enrolled women in a study to determine the effects of elective Cesareans for suspected big babies.

The clinical term for a big baby is Macrosomia. Macrosomia is defined as a baby weighing 4000 grams or at least 8lbs 13oz or more regardless of his or her gestational age.

When a baby cannot fit through the pelvis, this is called Cephalopelvic Disproportion (or CPD for short). While we might hear this term every now and again, true cases of CPD are actually pretty rare. In the 18th and 19th century, poor nutrition that resulted in rickets, and illnesses such as polio, lead to pelvic anomalies. These pelvic anomalies made CPD a somewhat common occurrence — one that resulted in loss of life during childbirth. As our nutrition and lifestyle have improved, pelvic anomalies have become rare. - See more on Cephalopelvic Disproportion at: https://www.bellybelly.com.au/birth/small-pelvis-big-baby-cpd/

Here are some important facts to mention:

  • 1 in 3 Women in America are being told their babies are too big, even though weight cannot be reliably predicted.

  • These same women are NOT being told that artificial induction methods and cesarean sections have not been shown to improve outcomes. In fact- these methods can even be harmful!

  • Suspected big baby (or macrosomia) is not a medical indication for induction or Cesarean, yet it is one of the most common reasons given for these procedures.

  • In 2014, the American College of Obstetricians and Gynecologists issued guidelines to care providers recommending that they limit interventions for suspected baby to “avoid potential birth trauma.”

  • Non-diabetic, low-risk women are NOT at higher risk of complications due to baby’s size. In some cases, such as with mothers who have pelvic deformities or uncontrolled gestational diabetes, a large baby can be a medical indication for intervention.

  • Ultrasound estimates of babies size are unreliable, especially at the end of pregnancy. Predictions of a big baby are right 50% of the time and wrong 50% of the time.

  • Statistically speaking, intervening due to a suspected big baby has been found to be more risky than the big baby itself and can lead to more complications.

  • It would take nearly 3,700 unnecessary Cesarean Sections to prevent one baby from having a permanent nerve injury due to shoulder dystocia.

  • About one in ten babies is born big in the United States (U.S.). Overall, 8.7% of all babies born at 39 weeks or later weigh between 8 lbs., 13 oz., and 9 lbs., 15 oz., and 1.7% are born weighing 9 lbs., 15 oz. or more (U.S. Vital Statistics). 

What is the bottom line?

In summary, for non-diabetic moms:

  • If a care provider predicts a big baby based on an ultrasound or physical exam, they will be wrong about half the time. Ultrasound weight results at the end of pregnancy can fall anywhere from 15% above or below the baby’s actual weight. 

  • About 7 to 15% of big babies have difficulty with the birth of their shoulders, which is known as shoulder dystocia. The chance of a permanent nerve injury due to shoulder dystocia is less common, happening in 1 out of every 555 babies who weigh between 8 lbs., 13 oz and 9 lbs., 15 oz, and 1 out of every 175 babies who weigh 9 lbs., 15 oz. or greater. Regular training is important for health care providers to keep up their skills in managing shoulder dystocia, as it can help prevent injuries. 

  • If a care provider thinks that you are going to have a big baby, this thought is sometimes more harmful than the actual big baby itself. This is because the suspicion of a big baby leads many care providers to manage a woman’s care in a way that increases the risk of Cesarean and complications.

  • Although a policy of very early induction (37 to 38 weeks) can prevent some shoulder dystocia cases from occurring, researchers have not been able to show that induction decreases the risk of brachial plexus palsy, and very early induction may carry other risks to the mother and baby. 

  • A policy of elective Cesareans for big babies likely does more harm than good for most women: It would take nearly 3,700 elective Cesareans to prevent one permanent case of brachial plexus palsy in babies who are suspected of weighing more than 9 lbs., 15 oz.

For mothers with diabetes or gestational diabetes:

  • Ultrasounds are slightly more accurate at predicting a big baby, because these moms are at higher risk of having a big baby to begin with

  • Elective Cesareans may be more cost-effective in women who have Type I or Type II diabetes than they would be in women without diabetes

  • Management of gestational diabetes (diet, exercise, or medication) lowers the chance of having a big baby and shoulder dystocia down to normal levels

For more information on this subject check out the following link: