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Risk of shoulder dystocia: associations with parity and offspring birthweight. A population study of 1 914 544 deliveries

Authors

  • EVA A. ØVERLAND,

    1. Department of Obstetrics and Gynecology, Akershus University Hospital and Institute of Clinical Medicine, Akershus University Hospital, University of Oslo, Lørenskog
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  • LARS J. VATTEN,

    1. Department of Public Health, Medical Faculty, Norwegian University of Science and Technology, Trondheim
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  • ANNE ESKILD

    1. Department of Obstetrics and Gynecology, Akershus University Hospital and Institute of Clinical Medicine, Akershus University Hospital, University of Oslo, Lørenskog
    2. Division of Mental Health, Norwegian Institute of Public Health, Oslo, Norway
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  • Please cite this article as: Øverland EA, Vatten LJ, Eskild A. Risk of shoulder dystocia: associations with parity and offspring birthweight. A population study of 1 914 544 deliveries. Acta Obstet Gynecol Scand 2012; 91: DOI: 10.1111/j.1600-0412.2011.01354.x

Eva A. Øverland, Department of Obstetrics and Gynecology. Akershus University Hospital, Postbox 24, 1478 Lørenskog, Oslo, Norway. E-mail: eva.overland@ahus.no

Conflict of interest
The authors have stated explicitly that there are no conflicts of interest in connection with this article.

Abstract 

Objectives. We estimated the associations of parity and offspring birthweight with the risk of shoulder dystocia, and studied whether the association of offspring birthweight differed by parity. Design. Population-based register study. Setting. The Medical Birth Registry of Norway was used to identify all deliveries between 1967 and 2006. Population. All vaginal deliveries of a singleton offspring in cephalic presentation during the period 1967–2006 (n=1 914 544). Main outcome measure. Shoulder dystocia at delivery. Results: Shoulder dystocia occurred in 0.68% (13 109/1 914 544) of all deliveries. There was a strong positive association of birthweight with risk of shoulder dystocia, and 75% (9765/13 109) of all cases occurred in deliveries of offspring weighing 4000g or more. The association of birthweight displayed similar patterns across parities, but the association was slightly stronger in parous than in primiparous women. Among first-time mothers, 0.12% (320/276 614) with offspring weighing 3000–3499g (reference) experienced shoulder dystocia, compared with 13.30% (169/1244) with offspring birthweight higher than 5000g [odds ratio (OR) 135.7, 95%CI 111.6–165.1]. The corresponding results for women with one previous delivery were 0.08% (161/201 572) and 16.45% (501/3054) (OR 246.4, 95%CI 205.4–295.5). Conclusions. High offspring birthweight is the major risk factor for shoulder dystocia, constituting most cases. The positive association of birthweight with shoulder dystocia showed similar patterns across parities, but high birthweight parous women were at greater risk of shoulder dystocia compared with primiparous women.

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