Think You Have A Big Baby?!

I recently read this article about evidence for induction or c-section for a big baby. I have known so many women that were advised to be induced or have a c-section and it’s frustrating to see this happen again and again. I’m hoping that through education, women can take back control of OUR births.

If you have the time, I suggest reading the full article. I have provided the main points for those that want to check out a brief summary of the article.

What is a big baby?

The medical term for big baby is macrosomia, which literally means “big body.” Some experts consider a baby to be big when it weighs more than 4,000 grams (8 pounds 13 ounces) at birth, and others say a baby is big if it weighs more than 4,500 grams (9 pounds, 15 ounces). A baby is also called “large for gestational age” if its weight is greater than the 90th percentile at birth (Rouse et al. 1996).

How common are big babies?

Big babies are born to about 1 out of 10 women in the 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).

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 4 major assumptions:

  1. Big babies are at higher risk for problems.
  2. We can accurately tell if a baby will be big.
  3. Induction keeps the baby from getting any bigger, which lowers the risk of C-section.
  4. Elective C-sections for big baby are beneficial and don’t have any major risks.

What is the evidence for these assumptions? Are they true? Let’s take a closer look at each one.

Assumption #1: Big babies are at higher risk for problems.

Reality #1: Big babies are at higher risk for temporarily getting their shoulders stuck, but difficulty giving birth to shoulders is unpredictable and permanent injuries are rare. A care provider’s suspicion of a big baby is more harmful than an actual big baby itself.

Assumption #2: We can tell whether a baby will be big at birth.

Reality #2: Care providers and ultrasound are equally poor at predicting whether a baby will be big at birth.

Assumption #3: Induction allows the baby to be born at a smaller weight, which helps avoid shoulder dystocia and reduces the risk of C-section.

Reality #3: Although suspected big babies who are induced are born about 3.5 ounces lighter, induction for suspected big baby does not lower the risk of shoulder dystocia, and it may increase the risk of C-section.

Assumption #4: Elective C-sections for big baby has benefits that outweigh the potential harms.

Reality #4: Among women who are not diabetic, it would take nearly 3,700 unnecessary C-sections to prevent one baby from having a permanent nerve injury due to shoulder dystocia. If care providers recommend an elective C-section for extra big babies (>9 lbs 15 oz), for every 3 cases of permanent nerve injury that they would prevent, there would be 1 extra maternal death.

What is the bottom line? In summary, for non-diabetic moms:

  • Ultrasounds and care providers are equally inaccurate at predicting whether or not a baby will be big. If an ultrasound or a care provider predicts a big baby, they will be wrong half the time.
  •  If a care provider thinks that you are going to have a big baby, this thought is more harmful than the actual big baby itself
    • The suspicion of a big baby leads many care providers to manage a woman’s care in a way that triples her risk of C-section and quadruples the risk of complications.
    • Because of this “suspicion problem,” ultrasounds to estimate a baby’s weight probably do more harm than good in most women.
  •  Induction for big baby does not lower the risk of shoulder dystocia and may increase the risk of C-section, especially in first-time moms
  • A policy of elective C-sections for big babies likely does more harm than good for most women
    • It would take nearly 3,700 elective C-sections to prevent one permanent case of nerve injury in babies who are suspected of weighing more than 9 pounds 15 ounces
    • For every 3 permanent nerve injuries that are prevented, there will be 1 maternal death due to the elective C-sections