Abstract
Osteogenesis imperfecta (OI) is an uncommon bone disorder caused by mutations in type I collagen involved in bone matrix leading to increased fracture risk. There are several sub-categories within OI, with OI type I being the most common and mildest form. Women with OI considering pregnancy need to be aware of bone loss and fracture risk, particularly with lactation. We report the first case of a female with twin pregnancy and OI type I who presented with multiple vertebral fractures following delivery and postpartum lactation. Following endocrine review, she weaned breast-feeding but represented within weeks with further pain and magnetic resonance imaging (MRI) demonstrating new T12 and L1 fractures. Even after receiving intravenous zoledronic acid, she experienced further thoracic pain after lifting, and MRI demonstrated a further T7 fracture. Following modification of her treatment regimen to daily teriparatide injections for 12 months, repeat dual-energy X-ray absorptiometry scan showed a significant improvement in bone mineral density at the lumbar spine and left hip. Bone loss with lactation is an important consideration for women with OI considering pregnancy. Women with OI should be assessed by an endocrinologist prior to conception to optimize bone health and have an individualized plan to mitigate bone loss and fracture risk during pregnancy and the postpartum period.