The Big Baby Conundrum

Photo from the New York Times

EMC’s Senior Writer and former labor and delivery nurse, Jeanne Faulkner, weighs in on a recent New York Times Well blog, “When a Big Baby Isn’t So Big.”

When I read the January 11th New York Times Well blog, titled When A Big Baby Isn’t So Big, I looked back on my career as a labor nurse and thought, “Yep — happens all the time.” Predictions for a “too big baby” were among the most common reasons I heard from women admitted to my labor unit for induction of labor or scheduled cesarean sections. In most cases, once the baby was delivered, either vaginally or surgically, they weren’t all that big after all.

The New York Times blog is centered around a recent study based on Childbirth Connection’s national survey of 1,960 new mothers, called Listening to Mothers III. The survey indicates that four out of five mothers who were warned they might have large babies gave birth to infants who were not large, and weighed less than 8 pounds 13 ounces (which defines macrosomia — a larger than average baby). These mothers were almost twice as likely to have interventions like medical induction of labor or attempt to self-induce labor, presumably so their baby wouldn’t get too big to deliver vaginally. They were also nearly twice as likely to have planned C-sections, though as the blog mentions, researchers say that increase fell just short of being statistically meaningful.

If so many “big babies” turn out to be normal size once they’re born and weighed, why do providers make false predictions? It starts during a routine prenatal visit when a mother’s belly is measured with a measuring tape, by the provider’s hands and/or the belly is scanned by an ultrasound. If measurements are larger than average, that might indicate a baby is large, but it might also indicate issues unrelated to fetal size like a high volume of amniotic fluid or poor maternal abdominal muscle tone. When a provider tells a patient, “your baby is getting too big,” a seed of doubt is sewn for a mother who is already nervous about potential injury during labor and birth. Few mothers understand that ultrasound estimates of fetal size can be off by as much as a couple pounds and that in most cases, it’s not a legitimate indication for induction or C-section.

According to guidelines to prevent primary C-sections (a mother’s first C-section) set by the American College of Obstetricians and Gynecologists and the Society for Maternal Fetal Medicine, it’s rarely appropriate to perform inductions or C-sections for a presumed big baby. Still, these interventions happen frequently. Why? We asked three obstetricians for their take on this all-too-common situation.

Richard Waldman, MD, an OB-Gyn in New York explains obstetricians’ biggest worries with extra-large babies.

“We have to be careful about taking information from a survey such as “Listening to Mothers” as medical fact. Nevertheless this is a real issue. When an obstetrician is told that the estimated fetal weight is larger than normal, he or she must inform the parents and discuss the risk of shoulder dystocia (a potentially dangerous birth complication where a baby’s head is delivered vaginally, but its shoulders are too large to fit through the birth canal). Once you start down that path parents often elect to have a C-section. I hated having the conversation for fear that mom would decide to have a C-section even when I was confident the baby would come out just fine vaginally. Brachial palsy injury to the newborn (a type of nerve injury) from shoulder dystocia is the second most common cause of malpractice claims for obstetricians. If you don’t mention the estimated weight and possibility of a shoulder dystocia then attorneys ‘get you.’ If you do mention it, you do unnecessary C-sections. Some obstetricians use the estimated fetal weight as way to talk mothers into C-sections to avoid all possible risks. But, that’s proven to be a mistake because inducing labor because of a suspected large fetus increases the risk of shoulder dystocia.”

Lynn Strickland, MD, an OB-Gyn in Los Angeles commented on the complexity of making that medical decision.

Many obstetricians have seen occasions where a C-section was recommended and performed for macrosomia only to find a smaller baby at delivery. It’s the clinical conundrum of medicine where the Hippocratic oath, “First, do no harm,” isn’t always black and white. In my opinion a more immediate solution lies in quality communication and patient counseling. While every situation is unique, offering a cautious trial of labor with a lower threshold for cesarean is an empowering option for some women.

Desiree Bley, MD, an OB-Gyn in Portland, OR encourages women to give labor a try, even if they think the baby is large.

“Term ultrasounds (done near a woman’s due date) have error rates of 20–30 percent, even by great sonographic technicians. Most women can deliver big babies vaginally just fine. One of my most formidable patients is a fabulous woman who pushed out a 12 pound 15.6 ounce boy. Her other babies ranged from 8–12 pounds. I tell my patient to be the amazing woman you are and give your body a chance. If the baby doesn’t fit, we’ll see that in labor or during the pushing stage. That’s when a cesarean might be a good option.”

Topics: Maternal Health 101s