Labour outcomes in siblings with congenital insensitivity to pain due to bi-alleleic scn9a mutations

Abstract

SCN9A codes for the voltage-gated sodium channel Nav1.7, a protein expressed most prominently in sensing pain neurons. Bi-alleleic loss of function mutations in SCN9A results in a severe ‘channelopathy’ associated with insensitivity to acute pain and anosmia. In this report we describe the labour and post-partum outcomes of two sisters with this trait belonging to a non-consanguineous Caucasian family living locally. Both gave a history of life long insensitivity to pain, anosmia and multiple previous unrecognised fractures. Neither sister experienced pain during labour; this had implications for the confidence of the midwifery teams' delivery of intrapartum care. Both delivered by caesarean section. During the post-partum period one of the sisters presented with sensory loss due to a spinal haematoma, a condition not previously associated with SCN9A abnormalities and the ensuing MRI revealed additional undiagnosed bilateral pelvic fractures. Both conditions were managed conservatively. The other sister had an uneventful recovery and both babies were well. These clinical consequences underline the important role of pain in labour management and in the puerperium for alerting staff to problems. This highlights the need for careful pre-pregnancy counselling, antenatal, intra-partum and post-natal management for any other women with this rare condition contemplating pregnancy.