We reviewed 1060 cases of OBPP prospectively at the Peripheral Nerve Injury Unit over 20 years. Data was collected for birth weight, maternal age, maternal height, maternal weight, duration of labour and associated difficulties, presentation, mode of delivery, neonatal problems, birth rank, race and social class.

The mean birth weight was 4.23 kg (Range 0.63–9.49 SD 0.72) compared to 3.47 Kg nationally [p < 0.05]. There was an association between severity of lesion and increase in birth weight.

Maternal age was 29.0 years in OBPP group [Range 14–43 SD 5.4] compared to 26.8 nationally [p < 0.05]. In 46.7% of the brachial plexus group, the mothers were > 30 years old. This was compared to 29.7% nationally.

The difference in maternal Body Mass Index (BMI) between patient group [27 with Range 14–44 SD 3.5] and national average of 25 was significant [p< 0.05]

Hypertension [11.8%] and diabetes [11.2%] were significantly [p< 0.05] higher than the national rate [6.4% and 1% respectively].

Shoulder dystocia occurred in 56% of the cases and was strongly associated with OBPP [p< 0.05].

Mean duration of labour nationally was 5.4 hours; in the patient group 10.8 hours [p< 0.05]

Breech presentation was more than three times the national average [p< 0.05]

Caesarean sections [2%] were less than national average [18%].

Instrumental deliveries [40.3%] were four times more than national rate. [P < 0.05]

The incidence of Neonatal asphyxia [22%] and Special Care Baby Unit [15.3%] was significantly [p< 0.05] higher than the national average [2% and 8% respectively]

Other factors did not prove to be statistically significant. These included; Social class, birth rank and ethnic origin.

We found that Birth weight, shoulder dystocia and body mass index are the most significant risk factors for obstetric brachial plexus plasy.