The vast majority of baptisms take place a few months after birth, allowing the new mother time to recover from childbirth, sleepless nights, etc...!
Although it is possible to be baptized at any age, the Catholic Church traditionally baptizes babies. It is the gift of God that is emphasized here. From a young age, the child is thus "adopted by the Father, incorporated into Christ, and inhabited by the Holy Spirit." Through baptism, they become a member of the Church.