BACKGROUND AND PURPOSE:

• Bushman et al. (American Journal of Perinatology, 2019) investigated whether knowledge of EFW ≥4,000g leads to shortened labor times

METHODS:

• Secondary analysis of a retrospective cohort study
• Participants
  • Singleton pregnancies ≥36 weeks
• EFW determined by
  • Ultrasound (US) within 3 weeks or
  • Physical exam on admission
• Exclusion criteria
  • Initial cervical exam was ≥6 cm or no attempt was made to labor
  • Comorbidities that would be expected to influence length of labor (e.g., hypertension)
• Patients were classified as
  • EFW of ≥4,000g
  • <4,000g
• Primary outcomes
  • Duration of labor
    • Evaluated as total time from 4 cm to delivery (with 4-cm dilation being a surrogate marker for active labor)
    • Length of time allowed from 4 cm until the first documented cervical change (or delivery)
    • Time in second stage of labor (complete dilation to delivery)
  • Cesarean delivery

Note: Active labor defined as >6 cm | 4 cm cut off used because at the research institution, foley is used for patients <4 cm

• Secondary outcome
  • Arrest of labor

RESULTS:

• 1,506 patients were included
  • 54 (3.5%) had EFW of ≥4,000g
• Women with documented EFW of ≥4,000g had greater
  • BMI | Likelihood of induction | Likelihood of an US within 3 weeks of delivery
• EFW of ≥4,000g was not associated with shortened labor times but was associated with increase risk for cesarean delivery
  • ≥4,000 g: 29.6%
  • <4,000 g: 9.3%
  • Adjusted odds ratio (AOR) 2.7 (95% CI: 1.3 to 5.5)
• EFW based on US rather than physical exam alone was not associated with shortened labor times but was associated with increased risk for cesarean delivery  
  • Ultrasound: 13.1%
  • External palpitation: 7.9%
  • AOR: 1.5 (95% CI, 1.01 to 2.12)

CONCLUSION:

• Knowledge of EFW ≥4,000g, especially based on ultrasound diagnosis, is not associated with shortened labor, but is associated with increased risk of cesarean delivery
• The results of this study suggest that the increased risk for cesarean is not a result of obstetricians shortening labor times because of concern for macrosomia
• The authors state  

Given these findings an EFW of ≥4,000g by external palpation or US appears to be an independent risk factor for cesarean delivery and can be used to guide labor management accordingly

Learn More – Primary Sources:

Influence of Estimated Fetal Weight on Labor Management

Related ObG Topics:

Macrosomia: Determination of EFW and Recommendations for Delivery

How Accurate are Estimated Fetal Weight Ultrasound Measurements between 23 and 25 Weeks?

Can Fetal Head Size Help Predict Risk of Cesarean Section?

Are New Predictors of Fetal Weight Superior to Traditional Ultrasound?