Brittle bone disease is the common name for osteogenesis imperfecta (OI). This is a group of genetic conditions characterised by bone fractures, spinal curvature and a slight blue tinge to the whites of the eyes. Depending on the severity of the condition, bone fractures can be very severe and disabling, or milder and only occuring with trauma. Most types are inherited through a dominant gene, which means that baby has a 50% chance of being affected. More specific details about genetic testing in pregancy can be obtained from a clinical genetics doctor, and you would quite possibly be offered extra ultrasound scans in pregnancy.