Shoulder dystocia occurs when there is a mechanical obstruction of the anterior fetal shoulder during the birthing process after the head is delivered. The basis of any litigation related to shoulder dystocia is – 1) Did they identify risk factors, and 2) Did they respond appropriately? In Part 1 of this series, we discussed some of the potential fetal and maternal injuries that can occur as a consequence of shoulder dystocia as well as some of the interventions utilized by providers once a shoulder dystocia is recognized.
Shoulder dystocia cannot be prevented, but there are several risk factors associated with an increased incidence of shoulder dystocia. The incidence of shoulder dystocia increases progressively as the infant’s birthweight increases over 4,000 grams (8# 13 oz.) and increases significantly when the birthweight is greater than 4, 500 grams (10#). However, it can be very difficult to accurately estimate fetal weight prior to delivery, and based on several factors – maternal obesity, location of fetus’s head in the pelvis, amount of fluid, and provider’s skill – the estimated fetal weight (EFW) can be off by 2 pounds either way. In a study of 7,859 infants with a birthweight greater than 5,000 grams (11 #), shoulder dystocia was reported in only 15.5% of deliveries ; 50% of all shoulder dystocias occur in infants weight less than 4,000 grams and without any identifiable risk factors.
Another risk factor is maternal obesity. This increases the risk for both gestational diabetes and higher neonatal birthweight. Pre-existing or gestational diabetes increases the likelihood of shoulder dystocia several fold over the non-diabetic population. Infants of diabetic mothers tend to have higher birthweights due to higher glucose levels. Also, the baby’s chests and shoulders are broader, increasing the risk for shoulder dystocia. Excessive maternal weight gain, greater than 25 pounds, increases the risk for gestational diabetes and increased fetal birthweight.
Women with a previous history of delivery complicated by shoulder dystocia have a recurrence rate of 10-25%. In all subsequent pregnancies, babies tend to get bigger, and mothers tend to weigh more. These factors combined increase the risk for a subsequent shoulder dystocia. Many women and their providers choose to deliver a subsequent baby by elective cesarean section following a complicated shoulder dystocia delivery which can alter the recurrence rates. The risk is also increased in post-term gestations past 41 weeks. The baby continues to grow and gain weight between 40 and 42 weeks. The risk for shoulder dystocia after 41 weeks gestation is increased by 30%.
Having a male fetus increases the risk slightly from 55% versus 51%. The birthweight among male infants is slightly higher than that of girls. In one study, 70% of infants with a birthweight greater than 4,500 grams (10#) were male. Male fetuses also tend to have broader chests and shoulders.
Abnormal labor progress can be a signal of impending shoulder dystocia. A rapid labor, less than 3 hours from beginning to end, can result in the baby coming through the pelvis too quickly and not allowing for the proper rotational movements needed to navigate the pelvis properly. A prolonged 2nd stage, or active pushing stage, can indicate that the baby is going to have an increased risk for shoulder dystocia. The generally accepted time limits to allow a woman to actively push (with a reassuring fetal tracing) is dependent on various factors, but usually falls within:
- 1st baby with an epidural >3 hours
- 1st baby without an epidural >2 hours
- 2nd baby or more with an epidural >2 hours
- 2nd baby or more without an epidural >1 hour
Maternal demographics can play a role in risk identification for shoulder dystocia. Age less than 16 or greater than 35 years are at increased risk and also at increased risk for the development of gestational diabetes. African American/Black women are at increased risk versus Caucasian/ White women. Short stature less than 5 feet increases the risk especially when combined with obesity.
Operative vaginal delivery with forceps or vacuum extractor increases the risk. This is the old “chicken before the egg” concept. Did the impacted shoulder keep the head from coming down into the pelvis causing the need for the instrumental delivery or, did the instrument cause the shoulder to become impacted? The greatest risk for shoulder dystocia is with prolonged 2nd stage, estimated fetal weight greater than 4,000 grams, and instrumental delivery.
It is common for women and their families who experience a vaginal delivery complicated by shoulder dystocia with a poor fetal or maternal consequence to wonder, “Why didn’t they just do a C-section and get the baby out?” Because shoulder dystocia is not preventable and is poorly predictable, a “prophylactic” cesarean section is rarely medically indicated or even offered by obstetrical providers. ACOG, The American College of Obstetricians and Gynecologists, state in their Practice Bulletin #178 on Shoulder Dystocia:
- Delivery before 39 weeks gestation is not recommended unless there are medical indications
- Elective cesarean delivery should be considered for the following:
- Without diabetes: estimated fetal weight of 5,000 grams or higher
- With diabetes: estimated fetal weight of 4,500 grams or higher
- Not suggested for fetal macrosomia (>4,000 grams) as induction has not been shown to improve maternal or fetal outcomes
- Trial of labor
- Suspected fetal macrosomia is not a contraindication to a trial of labor after cesarean section
Litigation in a shoulder dystocia case boils down to: 1) Did ALL the healthcare providers accurately identify any potential risk factors that might increase the incidence for shoulder dystocia, and 2) Did ALL the healthcare providers respond appropriately when the shoulder dystocia presented itself? This may involve standard of care issues during the prenatal period, labor, delivery, or even during the first few hours after the birth. In Shoulder Dystocia – Do You Have a Case? Part 3, we will discuss brachial plexus and hypoxic brain injuries.