Risk Factors for Recurrent Shoulder Dystocia, Washington State 1987-2004

1
Risk Factors for Recurrent Shoulder Dystocia,
Washington State 1987-2004

• Hillary Moore, MD
• University of Washington School of Public Health
  and Community Medicine
• Department of Epidemiology
• Maternal and Child Health Track
• Melissa Schiff, Thesis Advisor
• Susan Reed, Thesis Committee Member

2
Introduction

• Shoulder dystocia is an obstetric emergency in
  which an infants shoulders fail to deliver
  spontaneously after delivery of the head

3
Background

• Can result in significant infant morbidity and
  mortality as well as maternal morbidity
• Incidence of primary shoulder dystocia is
  0.13-1.16 of vaginal deliveries
• Four previous studies on recurrent shoulder
  dystocia
• Very small number of cases
• No adjustment for confounding
• Referral center populations

4
Specific Aims

• What are the incidences of primary and recurrent
  shoulder dystocia?
• What are the risk factors for recurrent shoulder
  dystocia?

5
Methods

• Data Source Washington State Longitudinal Birth
  Records Database linked with birth
  hospitalization discharge diagnoses, 1987-2004

6
Methods

• Calculated primary and recurrent shoulder
  dystocia annual incidences
• Described maternal characteristics of women with
  and without recurrent shoulder dystocia and a
  subsequent cesarean section
• Used logistic regression to calculate Odds Ratios
  (OR) and 95 Confidence Intervals (CI) for the
  following risk factors
• Birth weight
• Gestational age
• Body Mass Index
• Maternal weight gain
• Gestational Diabetes
• Operative assistance
• Induction of labor

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Methods

• Constructed a multivariable logistic regression
  model including maternal age and parity as
  confounding factors to obtain adjusted risk
  estimates for risk factors found to be
  significantly associated with recurrent shoulder
  dystocia
• Analysis was performed with stratification by
  diabetes status

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Results
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Results (continued)
Cases Controls Cesarean Section N1,060 N
4,238 N1,172 () () () Maternal Age
(years) lt20 2.0 3.7 1.6
20-24 19.4 23.1 16.1 25-29 33.1 31.1
30.0 30-34 30.3 27.2 32.6
35 15.2 14.8 19.6 Parity
1 42.5 63.5 50.6 2 32.6 20.3 28.9
3 12.4 8.1 10.1 4 4.6 3.0 4.8
5 4.9 1.9 3.2
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Results (continued)
Risk Factor Crude OR Adjusted OR (95
CI) (95 CI) Gestational diabetes in
subsequent pregnancy 1.5 (1.2,
2.0) 1.2 (0.9, 1.5) Birth weight in index
pregnancy (grams) lt2500 - -
2500-2999 0.4 (0.2, 0.7) 0.4 (0.2, 0.7)
3000-3499 Reference Reference
3500-3999 2.0 (1.6, 2.4) 1.9 (1.5, 2.4)
4000-4499 3.7 (3.0, 4.6) 3.5 (2.8, 4.4)
4500-4999 3.8 (2.8, 5.2) 3.3 (2.4, 4.5)
5000 6.5 (3.4, 12.6) 4.5 (2.2, 9.3)
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Results (continued)
Risk Factor Crude OR Adjusted OR (95
CI) (95 CI) Operative delivery in index
pregnancy Forceps 0.9 (0.7, 1.2) 1.1
(0.8, 1.4) Vacuum 1.2 (1.0, 1.4) 1.5
(1.3, 1.9) Both - - No operative
assistance Reference Reference Induction in
subsequent pregnancy 1.2 (1.0, 1.4) 1.1 (0.9,
1.3)
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Discussion

• Increasing magnitude of risk with increasing
  birth weight in the index pregnancy
• 50 increased risk of recurrence with vacuum
  assistance in the index pregnancy
• No significant association between gestational
  diabetes and recurrence after adjustment for
  maternal age and parity
• No effect modification by diabetes status
• Caesarean sections after primary shoulder
  dystocia
• Limitations

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Conclusion

• Based on our population-based study, birth weight
  and vacuum assistance in the index delivery
  indicate increased risk of recurrence in a
  subsequent delivery
• In the context of an increasing primary shoulder
  dystocia incidence, identification of risk
  factors for recurrent shoulder dystocia is needed
  for clinical decision-making

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Thank you

• Melissa Schiff
• Susan Reed
• Bill OBrien
• Sara Donahue and my MCH colleagues

Supported in part by Project T76 MC 00011from
the Maternal and Child Health Bureau (Title V,
Social Security Act), Health Resources and
Services Administration, U.S. Department of
Health and Human Services.