Maternal and anthropomorphic risk factors for shoulder dystocia.

OBJECTIVE

To study maternal and anthropomorphic parameters as potential risk factors for shoulder dystocia.

METHODS

From a series of 9667 vaginal deliveries between January 1998 and December 2003, a total of 138 cases complicated by shoulder dystocia were retrospectively identified and compared with a control group of 138 uncomplicated vaginal deliveries. In addition to maternal age, parity, diabetes, body mass index (BMI), and ethnicity, anthropometric factors including maternal height-to-infant weight ratio, characteristics of labor, management techniques, and outcome were evaluated as possible risk factors for shoulder dystocia.

RESULTS

The overall incidence of shoulder dystocia in this retrospective series of vaginal deliveries was 1.4%. In univariate analysis, maternal obesity (OR; 95% CI: 3.6; 2.1-6.3), diabetes (OR: 19.4; 2.5-145.7), parity greater than 2 (OR: 2.5; 1.4-4.4), maternal height-to-infant weight ratio (OR: 1.02; 1.01-1.04; P < 0.001), and infant weight-to-maternal BMI ratio (OR: 1.02; 1.01-1.03; P < 0.001) were predictive of shoulder dystocia. In multiple regression analysis, obesity and multiparity were the most significant maternal risk factors for shoulder dystocia. The only anthropometric factors associated with shoulder dystocia in multiple regression analysis were maternal height <1.55 m (OR: 6.6; 1.3-34.9) and maternal height-to-infant weight ratio (OR: 1.02; 1.01-1.05).

CONCLUSIONS

Shoulder dystocia may be anticipated in cases involving short women and discrepancy between maternal height or weight and infant weight.