Association of Fetal Abdominal–Head Circumference Size Difference With Shoulder Dystocia: A Multicenter Study

• Main Authors: Loraine Endres, Emily DeFranco, Theresa Conyac, Marci Adams, Ying Zhou, Kristin Magner, Luke O'Rourke, Kiley A. Bernhard, Danish Siddiqui, Anna McCormick, Jacques Abramowicz, Ronald Merkel, Rana Jawish, Mounira Habli, Alissa Floman, Everett F. Magann, Suneet P. Chauhan
• Format: Article
• Language: English
• Published: Thieme Medical Publishers, Inc. 2015-04-01
• Series: American Journal of Perinatology Reports
• Subjects: ultrasound; abdominal circumference; head circumference; shoulder dystocia
• Online Access: http://www.thieme-connect.de/DOI/DOI?10.1055/s-0035-1548544
• ISSN: 2157-6998; 2157-7005

Abstract Objective This study aims to determine if shoulder dystocia is associated with a difference in the fetal abdominal (AC) to head circumference (HC) of 50 mm or more noted on antenatal ultrasound. Study Design A multicenter matched case–control study was performed comparing women who had shoulder dystocia to controls who did not. Women with vaginal births of live born nonanomalous singletons ≥ 36 weeks of gestation with an antenatal ultrasound within 4 weeks of delivery were included. Controls were matched for gestational age, route of delivery, and diabetes status. Results We identified 181 matched pairs. Only 5% of the fetuses had an AC to HC of ≥ 50 mm. The proportion of AC to HC difference of ≥ 50 mm was significantly higher in shoulder dystocia cases (8%) than controls (1%, p = 0.002). With multivariate regression, the three significant factors associated with shoulder dystocia were AC to HC ≥ 50 mm (odds ratio [OR], 7.3; confidence interval [CI], 1.6–33.3; p = 0.010), femur length (OR, 1.1; CI, 1.0–1.2; p = 0.002), and induced labor (OR, 1.8; CI, 1.1–3.1; p = 0.027). Conclusion A prenatal ultrasound finding of a difference in AC to HC of ≥ 50 mm while uncommon is associated with shoulder dystocia.