Objective To investigate the nature and extent of neurosurgically treated obstetric plexus lesions with obstetric and neonatal precedents. Design Retrospective analysis of prospectively collected... Show moreObjective To investigate the nature and extent of neurosurgically treated obstetric plexus lesions with obstetric and neonatal precedents. Design Retrospective analysis of prospectively collected data. Setting Leiden, the Netherlands. Population A 9-year cohort of infants (n = 206) neurosurgically treated for obstetric brachial plexus lesion at a tertiary referral centre for nerve lesions. Method Obstetric and neonatal data (parity, diabetic status, pregnancy gestation, mode of cephalic delivery and birthweight) were collected using a standardised protocol and correlated to neurological severity of the brachial plexus lesion. Main outcome measure Neurological severity of the brachial plexus lesion. Results Nulliparous women delivered significantly lower birthweight newborns (P = 0.016), injuries in those infants were associated with the least severe injury classification. The most prominent association in ordinal logistic regression was between neurological injury severity and larger birthweight (P < 0.001). Conclusions Birthweight is correlated with neurological severity of the injury in a group of infants experiencing brachial plexus injury resulting from cephalic vaginal delivery. Show less