During the first year of life, your baby will grow and develop at an amazing speed. Major achievements are called developmental milestones and include rolling over, sitting up, standing and walking. Note that no two babies are exactly alike and your baby will most likely develop at his/her own pace. Most babies reach certain milestones at similar ages, but it's not unusual for a healthy, “normal” baby to develop more slowly of faster at certain stages. The following milestones are only guidelines. Your baby's doctor will evaluate your baby's development at each hospital visit. You can always talk to your child's doctor if you think your baby is lagging behind. Babies born prematurely (before 37 weeks of pregnancy), may develop more slowly. Ideally, the age at which your baby is expected to reach various milestones is based on her due date, not her birthday. A baby born two months early, will most likely achieve developmental milestones two months later than expected.