Children grow in a natural sequence, although each child grows and gains skills at his or her own pace, but at 18 months of age, children will reach certain milestones. Parents need to know the developmental milestones to monitor and care for their 18-month-old children. Children grow in a natural sequence, although each child grows and gains skills at his or her own pace, but at 18 months of age, children will reach certain milestones. Parents need to know the developmental milestones to monitor and care for their 18-month-old children comprehensively in all areas.