Source

Baylor College of Medicine, Department of Obstetrics and Gynecology, Houston, Texas; St. Mark's Hospital, Salt Lake City, Utah. belfort@bcm.edu.

Abstract

OBJECTIVES:

We evaluated whether fetal cranial shape was related to shoulder dystocia.

STUDY DESIGN:

We compared shoulder dystocia cases (n = 18) to controls (normal vaginal deliveries, n = 18) in a retrospective matched-pairs observational study. Subjects were matched for known maternal and fetal risk factors and then evaluated for fetal biometric differences measured by ultrasound near delivery. We tested multivariate risk models to predict shoulder dystocia by logistic regression.

RESULTS:

Cases had a shorter estimated occipitofrontal diameter (OFD) (p = 0.02) and larger biparietal diameter/estimated OFD ratio (p = 0.003). A multivariable model including estimated fetal weight, estimated OFD, maternal weight, and diabetes mellitus had a sensitivity and specificity of 86%/95%, and positive and negative likelihood ratios of 18.9/0.15. Estimated OFD significantly increased the predictive value of the model.

CONCLUSION:

Short estimated OFD is a risk factor for shoulder dystocia in the presence of other significant risk factors. A multivariable model including estimated OFD can predict shoulder dystocia in a clinically useful range. Copyright © 2011 ISUOG. Published by John Wiley & Sons, Ltd.