When is a Baby Too Big to be Born Vaginally?

The New York Times magazine spread on midwife Ina May Gaskin is drawing lots of attention. In it, Samantha M. Shapiro gives a balanced summary of Ina May Gaskin’s contributions to obstetrics, midwifery and the home birth movement. But then on the last page, Shapiro tells her own birth complicated birth story and some questions about c-sections and big babies emerge.

“When I reached my due date, an ultrasound estimated that my baby weighed 9.4 pounds. I didn’t have gestational diabetes and had gained an average amount of weight, and fetal tests showed my baby was thriving. But the baby’s estimated size, combined with the fact that he hadn’t yet descended into my pelvis, worried my midwife. She wanted the baby out by 41 weeks, and to my surprise, she suggested I consider going straight to surgery without labor. She sent me to be evaluated by a doctor she worked with. ‘One way or another, this baby will be a C-section,’ he said.”

She tried to get labor going and was successful but in the end her care-providers were adamant, she had the c-section.

Is 9lb, 4oz really too big to be born vaginally??

The answer is clearly not “yes” because so many babies are born over 9 lbs (all four of my mothers children including me, for starters.) But let’s look at the data:

First, what is big?

“Fetal macrosomia” is the official terminology for a big baby and according to the American College of Obstetricians and Gynecologists (ACOG):  “Results from large cohort studies support the use of 4,500 g (9lb,4oz.) as the weight at which a fetus should be considered macrosomic.”

Why is a big a concern? The baby’s shoulder could get stuck during the second stage (pushing the baby out)– this is called shoulder dystocia. This is more likely with macrosomic babies but it also happens randomly with small babies. (Positioning plays a role, too.)

So should all babies over 9lbs, 4 oz be delivered via c-section?

Not according to ACOG:

Recommendations based on good and consistent scientific evidence (Level A):

  • The diagnosis of fetal macrosomia is imprecise. For suspected fetal macrosomia, the accuracy of estimated fetal weight using ultrasound biometry is no better than that obtained with clinical palpation (Leopold’s maneuvers).

Recommendations based on limited or inconsistent scientific evidence (Level B):

  • Suspected fetal macrosomia is not an indication for induction of labor, because induction does not improve maternal or fetal outcomes.
  • Labor and vaginal delivery are not contraindicated for women with estimated fetal weights up to 5,000 g [11 lbs] in the absence of maternal diabetes.
  • With an estimated fetal weight more than 4,500 g, a prolonged second stage of labor or arrest of descent in the second stage is an indication for cesarean delivery.

Recommendations based primarily on consensus and expert opinion (Level C):

  • Although the diagnosis of fetal macrosomia is imprecise, prophylactic cesarean delivery may be considered for suspected fetal macrosomia with estimated fetal weights of more than 5,000 g [11 lbs]  in pregnant women without diabetes and more than 4,500 g [9 lbs, 4oz]  in pregnant women with diabetes.
  • Suspected fetal macrosomia is not a contraindication to attempted vaginal birth after a previous cesarean delivery.

Over at the blog The Heidi Hypothesis there’s an excellent breakdown of this issue with a quote from Amy Romano, CNM and  co-author of Optimal Care In Childbirth. She says:

“Some birth injuries would be averted if all women with suspected macrosomia had c-sections, but the number needed to treat is in the thousands. (Thousands of women would need to have c-sections to prevent one permanent injury related to shoulder dystocia).”

I can’t begin to speculate what was going on with Shapiro’s birth but I do find there’s a lot of confusion about what to do if the baby is “big.” Shapiro never tells us what the weight of her newborn was after the c-section– was her baby, in fact, big? Estimates can be off a full pound in either direction. I’d be interested to know.

What has your doctor told you about the size of your baby?


Article Posted 6 years Ago

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