Can My Doctor Really Predict Shoulder Dystocia?
“I’m 36 weeks and the ultrasound said that my baby is going to be nine pounds! My doctor says I might need to get used to the idea of having a c-section because the baby might grow too big for me.”
“My doctor scheduled me a cesarean because the ultrasound said that the baby is already ten pounds and he says I am at risk of shoulder dystocia.”
As the cesarean rate around the world skyrockets, women are turning to message boards on a daily basis with the same story: late-term ultrasound, recommendation of cesarean for big baby, doctor says shoulder dystocia might occur if I deliver this baby vaginally, I scheduled the c-section. Occasionally women will question others on the message board about the validity of their doctor’s shoulder dystocia prediction abilities.
In addition to asking other women to share their experiences, reading a page from a recent obstetrics textbook might be helpful. The following quote is from page 140 of Munro-Kerr’s Operative Obstetrics (2007) by Baskett, et. al.:
Unfortunately, attempts to find factors that will accurately predict shoulder dystocia and allow a practical prevention strategy have been unsuccessful. Most of the antepartum risk factors have fetal macrosomia as the underlying theme. Many of these risk factors are common, while the condition they predict, shoulder dystocia, is not. Furthermore, the risk of serious fetal injury associated with shoulder dystocia is rare. The hope that ultrasound prediction of fetal weight and more detailed ultrasound measurements such as shoulder width would provide an accurate level of risk have been unfilled. Indeed, for the macrosomic fetus clinical estimation of fetal weight is as accurate as that predicted by ultrasound. Even if one could predict fetal macrosomia accurately, it would be of limited value. About 95% of infants weighing over 4000 grams will not have shoulder dystocia. It has been suggested that elective caesarean for fetuses weighing more than 4500 grams would reduce shoulder dystocia and fetal injury. A decision analysis model has shown that this strategy would be both clinically and cost ineffective; it was estimated that to prevent one permanent brachial plexus injury 3695 caesarean sections would be required. Furthermore, the majority of cases of shoulder dystocia occur at fetal weight less than 4500 grams.
Thus, both the antepartum and intrapartum risk factors lack sensitivity and specificity. Having said that, there are individual cases with cumulative risk factors such as maternal diabetes and estimated fetal weight > 4250 grams which may be best delivered by caesarean section. A combination of factors such as clinical fetal macrosomia with a protracted late first stage of labour and slow descent in the second stage requiring assisted mid-pelvic delivery may dictate that caesarean delivery would be more prudent.
Refusal of a doctor’s recommendation of a prophylactic cesarean without suffering coercion and deceit should be regarded as a fundamental right of the pregnant woman.