 The first three years of every child's life are critical. Learn more about early intervention. How your baby or toddler plays, learns, talks, acts, and moves give important clues as to how they are developing. If you have any questions or concerns about whether your baby or toddler's development is on track, please call 1-800-515-BABY. That's 1-800-515-2229. Call 1-800-515-BABY. That's 1-800-515-2229.