Final answer:
A newborn should be given a sponge bath until their umbilical cord stump falls off, which typically happens within 1 to 4 weeks after birth.
Step-by-step explanation:
A newborn should be given a sponge bath until their umbilical cord stump falls off, which typically happens within 1 to 4 weeks after birth. Until the stump falls off, it is important to keep it clean and dry to prevent infection. After the umbilical cord stump falls off, the baby can be given regular baths.