Association of fetal cranial shape with shoulder dystocia

• Published in: Ultrasound in obstetrics & gynecology 2012-03, Vol.39 (3), p.304-309
• Main Authors: Belfort, M. A., White, G. L., Vermeulen, F. M.
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Case-Control Studies; Cephalometry; Delivery, Obstetric - adverse effects; Delivery. Postpartum. Lactation; Diseases of mother, fetus and pregnancy; Disorders; Dystocia - diagnostic imaging; Dystocia - etiology; Female; Fetal Weight; Frontal Bone - abnormalities; Gynecology. Andrology. Obstetrics; Humans; Medical sciences; multivariable prediction; Multivariate Analysis; Occipital Bone - abnormalities; occipitofrontal diameter; occipitofrontal diameter/biparietal diameter ratio; Predictive Value of Tests; Pregnancy; Pregnancy in Diabetics; Pregnancy Outcome; Pregnancy. Fetus. Placenta; Retrospective Studies; Risk Factors; Sensitivity and Specificity; Shoulder; shoulder dystocia; shoulder dystocia prediction; Skull - abnormalities; Skull - diagnostic imaging; Ultrasonography
• ISSN: 0960-7692; 1469-0705
• DOI: 10.1002/uog.9066

Objective To evaluate whether fetal cranial shape is related to shoulder dystocia. Methods We compared shoulder dystocia cases (n = 18) with 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, which were measured by ultrasound near delivery. We tested multivariable risk models to predict shoulder dystocia by logistic regression. Results Cases had a smaller estimated occipitofrontal diameter (OFD) (P = 0.02) and a larger biparietal diameter/estimated OFD ratio (P = 0.003). A multivariable model including estimated fetal weight, estimated OFD, maternal weight and diabetes mellitus had sensitivity and specificity of 86% and 95%, respectively, and positive and negative likelihood ratios of 18.9 and 0.15, respectively. Estimated OFD significantly increased the predictive value of the model. Conclusion A small 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 © 2012 ISUOG. Published by John Wiley & Sons, Ltd.