There are four primary types of OI a person can get. According to the Cleveland Clinic, Type I is the most common, and it is also the mildest form of the disease. The source says that these individuals will often experience “more fractures during childhood than adulthood.” Type II is the most severe form of OI, where fetuses may develop bent or fractured bones while in the womb. As a result, most do not survive birth or, if they do, die shortly after.
With Type III, which is also very severe, babies are often born with broken or deformed bones, which Healthline.com says “may get worse as your child gets older.” Type IV can range in severity from mild to severe, but most bones fractures tend to occur before puberty.