How I Would Counsel a Woman with a Suspected Large Baby


Guest post by an anonymous OB-GYN 



The prompt:

Suppose that tomorrow you were faced with a woman in a similar situation, and an estimated fetal weight of 10 pounds. Would you offer her an elective C-section? Why or why not? How would you counsel her about the risks? Could you do that without mentioning the risk of death? In what way would that be different than playing the “dead baby card?” Please tell me the specific language that you would use as a doctor. Mother has diet controlled gestational diabetes and otherwise uncomplicated pregnancy.


My first response is that I want more information. Was this her first pregnancy? If not what were the weights of her previous newborns?  How much did she and her husband weigh at birth? Where did the estimated fetal weight come from?  If, as I suspect, it is simply the result of a term US, then I would be inclined to ignore it entirely.

The estimated fetal weights derived from ultrasound are routinely incorrect by a factor of 10% across the board and those errors are higher in term mothers with excessive weight gain and much higher in mothers with BMI greater than 25.  At forty weeks gestation, that translates to over 2 pounds in an average size fetus and over three pounds in a larger fetus, i.e.: an 8 pound fetus is likely to be estimated as a ten pounder while a 9 pound fetus risks being estimated at 11 1/2 pounds or even twelve pounds. The larger the fetus, the greater the error.

How have the fundal heights been? We religiously collect this data during prenatal visits for a reason. It has better predictive value than a third trimester US. Has the growth curve according to fundal height been steady or has it accelerated in the third trimester?

How was gestational diabetes diagnosed? How well have her blood sugars been controlled? How much weight has she gained?

How was her gestational age (GA) determined?  Did she have regular menses prior to conceiving? What is the length of those cycles? Does she know without question when her last normal menstrual period began? Did she have any bleeding following her LNMP?

Did she have an early US that confirmed her gestational age?  Was that US abdominal or vaginal. Was her GA determined by an US at any point and if so when? Was that US done by an obstetrician, midwife, or US technician with experience in obstetrical ultrasound?

All of this information should be factored in to properly counsel a woman in this situation.



How would I counsel her without that information?

There is always a possibility that you could have difficulty delivering your baby’s shoulders, which are generally the widest part of the baby to get through your pelvis. That is true with every woman and every baby. We refer to this as a shoulder dystocia.

The risk of a shoulder dystocia is around 1% with babies less than 4000 grams but increases to 5% in babies greater than 4000 grams and higher as weights increase. Most women will not experience a shoulder dystocia even with babies greater than 5000 grams. In women who do experience shoulder dystocias most of those infants are delivered without incidence. Between 5 and 15 % of infants experiencing shoulder dystocia may have a brachial plexus palsy, which is nerve damage that limits mobility of the affected arm.  Ninety percent of those resolve without treatment within 12 months.

The single most common risk factor for shoulder dystocia is the use of vacuum extractors or obstetrical forceps to facilitate delivery.  Other risk factors include: known abnormal pelvic anatomy, poorly controlled gestational diabetes, post-dates pregnancy, previous shoulder dystocia, and short maternal stature.

However, most cases of shoulder dystocia occur in normal weight infants and are unanticipated. Because of this, identifying risk factors has not been shown to have any clinical usefulness.

No evidence exists to support induction in mothers who have gestational diabetes and suspected fetal macrosomia. Induction has been shown to increase rates of cesarean delivery, increase rates of newborn respiratory distress, but has not been shown to decrease rates of shoulder dystocia, or to have any impact on the risk of maternal or neonatal injury.

Elective cesarean delivery likewise is not recommended in cases of suspected fetal macrosomia.  It is estimated that 2,345 cesarean deliveries would be required to prevent one case of permanent brachial plexus injury.  That number may be somewhat smaller in women with both gestational diabetes and suspected fetal macrosomia but there remains no evidence that elective cesarean produces better maternal or neonatal outcomes.

If we were to encounter a shoulder dystocia during your delivery then there are a number of maneuvers that might be employed to complete the delivery. We might ask you top change positions, squat or get on your hands and knees. We might put some pressure above your pubic bone to attempt to dislodge your baby’s shoulder.  We might attempt to rotate the baby’s shoulder manually to dislodge it and to deliver one of the baby’s arms to reduce the thoracic diameter. In severe cases we may intentionally break the baby’s clavicle to reduce the bi-thoracic diameter. This will generally heal without difficulty.  In extremely rare and severe cases we must make more room to get the baby safely through the pelvis. That is best done by injecting local anesthesia into your pubic mons and using a scalpel to cut through the cartilage holding the two halves of the pubic bone together thus allowing the bony pelvis to expand.  This will normally heal without difficulty but may require a temporary brace to facilitate walking until healed.

There is a large body of data that suggests the mother and baby have a higher risk of post natal complications from a cesarean including maternal hemorrhage, hysterectomy, post operative and nosocomial infection, increased difficulties with bonding, post partum depression, and breastfeeding - all of which carry there own sets of future complications,  increased risks of maternal death both with the index pregnancy and more so with future pregnancies, bowel obstruction, placenta previa, placental accreta, vasa previa, and uterine rupture with subsequent pregnancies.

Babies have a higher risk of respiratory difficulties not only in the immediate post operative period but well into adulthood. They have increased rates of asthma, and recently recognized: increased rates of bronchiolitis (birth to 24 months for elective C/S) and pneumonia (12 to 24 months “emergent C/S”), and a huge array of cesarean complications that have been widely reported.

There is no evidence that offering someone a trial of labor produces worse outcomes.



And in answer to the additional question:


“What do you all think about the fact that the woman involved wasn’t counseled about the possibility of a large baby having a possibly difficult delivery and the option of a C-section?”

Every woman who has ever gone into labor since the beginning of time has “the possibility of a large baby (sic) having a possibly difficult delivery…”  Every woman who delivers in the United States has the option of a C-section – but there is not one shred of evidence that that C-section improves her outcome or her baby’s outcome. For the 10,000th time – first do no harm. If you can’t demonstrate with a reasonable degree of significance that doing an intervention actually improves outcomes then you should not be doing it.