Risk factors for shoulder dystocia-related brachial plexus injuries: A case-control study

Brachial plexus injury (BPI) is one of the major complications associated with shoulder dystocia. This study aimed to identify risk factors for shoulder dystocia-related BPI (SD BPI) in the Finnish population.

The study included all deliveries in the Hospital District of Helsinki and Uusimaa between 2006 and 2015 (n = 181 352). Singleton deliveries complicated by shoulder dystocia, BPI, and clavicle fracture were identified using ICD-10 codes O66.0, P13.4, P14.0, and P14.1 (n = 1708). Following a thorough review of medical records, 374 cases of BPI were identified, 259 of which were related to shoulder dystocia. The background-matched control group (n = 566) consisted of singleton deliveries without BPI.

The incidences of both BPI with and without shoulder dystocia declined significantly during the study period, from 0.16% to 0.05% and from 0.09% to 0.03%, respectively. Multivariate analysis identified the following independent risk factors for SD BPI: birthweight ≥4000 g (adjusted odds ratio, aOR 15.3), maternal diabetes (aOR 4.0), vacuum extraction (aOR 3.7), and maternal height ≤160 cm (aOR 2.7). A predictive model based on these four risk factors demonstrated a positive predictive value of 48.2% and a negative predictive value of 92.9% for SD BPI cases. The odds of permanent BPI were 2.5-fold for cases associated with shoulder dystocia compared to those without. Antepartum and intrapartum variables were not predictive of permanent SD BPI. Among all BPI cases, 69.3% were associated with shoulder dystocia and 64.2% with birthweight ≥4000 g.

Birthweight ≥4000 g, maternal diabetes, height ≤160 cm, and vacuum extraction independently increased the risk of SD BPI. Notably, 14.7% of all BPI cases occurred in the absence of both shoulder dystocia and birthweight ≥4000 g.