Can shoulder dystocia be predicted? Preconceptive and prenatal factors.

OBJECTIVE

To evaluate the predictability of shoulder dystocia using preconceptive and prenatal risk factors.

METHODS

Data from 1,622 term patients with prenatal care prior to 20 weeks who delivered single, vertex fetuses during a consecutive 12-month period were analyzed. Two groups were chosen. The first group was patients whose fetuses experienced shoulder dystocia during delivery (cases). The second group (controls) consisted of the remaining patients, whose fetuses had not experienced shoulder dystocia. The two groups were compared with regard to demographics and pregnancy characteristics.

RESULTS

Factors not significantly different between the two groups included were obesity, multiparity, history of diabetes, short maternal stature, postdatism and advanced maternal age. The incidence of macrosomia was significantly higher (P < .001) in cases (35.4%) than in controls (4.8%). Other factors associated with shoulder dystocia were previous shoulder dystocia, concurrent diabetes, prior delivery of a fetus > 4,000 g and excessive weight gain during pregnancy. Many factors previously associated with shoulder dystocia were found to be nonsignificant in our study.

CONCLUSIONS

Macrosomia appears to be the single important factor associated with shoulder dystocia which, even in the presence of significant risk factors, remains largely unpredictable.