Are there modifiable risk factors that may predict the occurrence of brachial plexus injury?

To identify risk factors, particularly modifiable, associated with brachial plexus injury.

A retrospective case-control study conducted at a single hospital between the years 1993 and 2012. All neonates who were diagnosed of brachial plexus injury were included. A control group matched at a ratio of 1:2 was randomly selected. Demographic and obstetric data were obtained from the hospital discharge register with ICD-9 codes and crosschecked with the labor medical records. All medical files were manually checked and validated. A stepwise logistic regression model was performed to identify independent predictors for brachial plexus injury before delivery among those found significant in the univariate analysis.

Of all 83 806 deliveries that took place during this period, 144 cases of brachial plexus injury were identified (1.7/1000 deliveries). Overall, 142 cases and 286 controls had available data. Among the study group, 41 (28.9%) had documented shoulder dystocia compared with 1 (0.4%) among the controls (P<0.0001). Logistic regression analysis revealed that maternal age above 35 years (P=0.01; odds ratio (OR) 2.7; 95% confidence interval (CI) 1.3 to 5.7), estimated fetal weight before delivery (P<0.0001; OR 2.5; 95% CI 1.7 to 3.8, for each 500 g increase), vaginal birth after cesarean (P=0.02; OR 3.3; 95% CI 1.2 to 8.8) and vacuum extraction (P=0.02; OR 3.6; 95% CI 1.2 to 10.3) were all found to be independent predictors for developing brachial plexus injury. When stratifying the analysis according to parity, vacuum delivery was found to be an independent risk factor only among primiparous women (OR 6.0; 95% CI 1.7 to 21.6).

The findings suggest that very few factors contributing to brachial plexus injury are modifiable. For that reason, it remains an unpredictable and probably an unavoidable event.