May 29th, 2022

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Correlation of Increased Fetal Asymmetry with Shoulder Dystocia in the Nondiabetic Woman with Suspected Macrosomia
Authors:  Priya V. Rajan, M.D., Judith H. Chung, M.D., Manuel Porto, M.D., and Deborah A. Wing, M.D.
  OBJECTIVE: To determine if the sonographic difference of ?2.6 cm between the fetal abdominal diameter (AD) and biparietal diameter (BPD), a proxy for fetal asymmetry, has an association with shoulder dystocia in nondiabetic women with suspected macrosomia.

STUDY DESIGN: A retrospective cohort study was performed in 3 Southern California tertiary care hospitals. We identified patients in whom sonographic evaluation after 36 weeks‘ gestation demonstrated an estimated fetal weight >4,000 g. Additional prenatal and delivery information was obtained from hospital records.

RESULTS: We identified 159 subjects who met ultrasound criteria and underwent a vaginal delivery. The mean AD-BPD difference in the shoulder dystocia group was significantly greater than in the group without shoulder dystocia (2.76±0.59 vs. 2.37±0.56, p=0.001). The adjusted OR of shoulder dystocia in the group with an AD-BPD difference ?2.6 was 3.67 (95% CI, 1.44-9.36).

CONCLUSION: Significant discordance between the fetal head and abdomen appears to be associated with an increased rate of shoulder dystocia in a nondiabetic population with suspected macrosomia. (J Reprod Med 2009;54:478-482)
Keywords:  biometry, fetal macrosomia, shoulder dystocia, ultrasonography
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