Shoulder dystocia is a rare obstetric emergency placing the mother and the fetus at risk for significant morbidity and mortality. It is diagnosed when after delivery of the fetal head further expulsion of the fetus is prevented by impaction of the fetal shoulders within the maternal pelvis (Figure 164-1).1 Shoulder dystocia is considered an emergent situation. The Emergency Physician must be able to recognize the condition and quickly respond. The goal is to deliver the fetus as quickly as possible using safe maneuvers and documenting the chain of events.
The head may retract toward the perineum (i.e., turtle sign) when delivery of the fetal head is not followed by delivery of the shoulders.
The incidence of shoulder dystocia varies due to the subjective nature of the diagnosis and the dependency on the documentation. It has been reported in up to 4% of cephalic spontaneous vaginal deliveries.2-7 Differing definitions of shoulder dystocia may account for some of this variability. Some reports require that maneuvers for shoulder release be documented on the chart whereas others accept the clinical diagnosis of shoulder dystocia. Other definitions look at the timing of the delivery of the head in relation to the delivery of the shoulders or the completion of the birth. The rare occurrences of shoulder dystocia make designing prospective studies difficult in describing the incidence and in evaluating the efficacy of various release maneuvers.8
Shoulder dystocia is most often unpredictable and unanticipated because accurate methods of predicting do not exist. Risk factors that increase the risk for shoulder dystocia are documented in the literature (Table 164-1). Many patients with shoulder dystocia do not have risk factors. Emergency Physicians may not have access to the patient’s prenatal history and/or ultrasound reports that may highlight the presence of risk factors for shoulder dystocia. It is therefore imperative for the Emergency Physician to be knowledgeable and comfortable with the various release maneuvers if shoulder dystocia is encountered during a precipitous delivery.9
TABLE 164-1The Risk Factors for Shoulder Dystocia ||Download (.pdf) TABLE 164-1The Risk Factors for Shoulder Dystocia
|Antepartum ||Intrapartum |
|Abnormal pelvic anatomy ||Arrested dilation |
|Advanced maternal age ||Assisted delivery (forceps or vacuum) |
|Diabetes (actual or gestational) ||Descent arrested, failed, or protracted |
|Excessive weight gain ||Labor augmentation (e.g., oxytocin) |
|Fetal macrosomia ||Pelvimetry concerning for cephalopelvic disproportion |
|Male fetus ||Prolonged labor of first stage |
|Maternal obesity ||Prolonged labor of second stage |
|Multiparity || |
|Previous large baby || |
|Previous shoulder dystocia || |
|Prolonged pregnancy || |
|Short maternal stature || |
ANATOMY AND PATHOPHYSIOLOGY
Shoulder dystocia is usually diagnosed after delivery of the fetal head when the fetal shoulders fail to deliver despite standard gentle traction on the fetal head. It results from impingement ...