Can delivering a baby before the next uterine contraction increase the risk of shoulder dystocia?

Delivering Before the Next Contraction and Shoulder Dystocia Risk

Attempting to deliver a baby before the next uterine contraction may increase the risk of shoulder dystocia, as physiologic birth typically occurs in two steps with a natural pause between head delivery and body delivery. 1

Understanding the Relationship Between Contractions and Shoulder Dystocia

• The two-step delivery process (head delivery followed by a pause until the next contraction delivers the body) should be considered physiologically normal and may actually help prevent shoulder dystocia 1
• Uterine contractions create the primary driving force for propelling the fetus through the birth canal, supplemented by maternal expulsive efforts during the second stage 2
• Attempting to deliver the fetal head during a uterine contraction can exacerbate problems with elevating the head, particularly in cases where there is already difficulty with delivery 2

Risk Factors for Shoulder Dystocia

• Shoulder dystocia is largely unpredictable, occurring in 0.15% to 2% of all vaginal deliveries 3
• Major risk factors include:
  • Fetal macrosomia (especially with estimated fetal weight >4500g with maternal diabetes or >5000g without diabetes) 2, 4
  • Maternal diabetes (increases risk of macrosomia and shoulder dystocia) 2
  • Previous shoulder dystocia 3, 4
  • Prolonged second stage of labor 3
  • Prolonged deceleration phase (from 8-10cm to complete dilation) 2
  • Operative vaginal delivery (forceps or vacuum) 3

Physiologic Birth Process and Shoulder Dystocia

• Natural birth typically involves a pause between head delivery and body delivery, allowing for:

  • Fetal rotation to align shoulders with the pelvic diameter 1
  • Maternal tissues to accommodate the shoulders 1
  • Uterine forces from the next contraction to assist with shoulder delivery 1

• Rushing delivery by applying traction before the next contraction may:

  • Interfere with the natural rotation of the shoulders 1
  • Increase the risk of shoulder impaction against the pubic symphysis 3
  • Lead to excessive force being applied, potentially causing brachial plexus injuries 3, 5

Management Recommendations

• When the fetal head delivers:

  • Consider allowing a pause until the next contraction rather than immediately applying traction 1
  • Avoid excessive downward traction on the fetal head 5
  • Be prepared to recognize shoulder dystocia if it occurs 5

• If shoulder dystocia is encountered:

  • The McRoberts maneuver (maternal thigh hyperflexion) is recommended as the initial procedure 2, 3
  • Suprapubic pressure can be applied as an adjunct to the McRoberts maneuver 3, 5
  • Additional maneuvers may be necessary if initial attempts fail 5

Clinical Implications

• Labor and delivery teams should be prepared to recognize and manage shoulder dystocia as it often occurs without warning 5
• Training and simulation exercises improve team performance when shoulder dystocia occurs 5
• The definition of shoulder dystocia may need reconsideration if we accept that a two-step delivery process with a pause between head and body delivery is physiologically normal 1