Milestones are developmental landmarks the baby shows as it gets older. Based on the expected milestones, you can determine whether the baby is developing normally. These milestones are however very variable. They can vary from child to child. In premature birth (when the baby's age is not corrected for gestational age ie. allowing them extra time which they would have in the womb) or when there is a medical problem (eg cardiac) the milestones can be delayed. A family history of delayed development can also lead to developmental delay, which may be a normal variation or due to a genetic abnormality in the family. In this situation please consult your doctor if you are worried.