Why Is Rapunzel Held Captive By The Witch?

The name "Rapunzel" derives from "rapun" or radish. A pregnant woman develops a craving for radishes and ventures into the garden of a witch to steal some. The witch catches  her and demands, in exchange for the mother's life, to be given the baby when it is born. In due course, little Rapunzel is sent to her, and grows up in the witch's house. She has very long hair, and the witch uses this as a rope ladder; every evening she comes home, calls out "Rapunzel, let down your hair!" and climbs up it. One evening this is secretly observed by a young man; at the next opportunity, he imitates the witch's voice, climbs the hair and meets Rapunzel. In some versions, these meetings go on long enough for Rapunzel to become pregnant; in the one usually given to children, the witch soon finds out, cuts off the hair, lures the lover to climb it and then lets him fall. He falls in a thorn bush and is blinded.
The usual ending to the story is that Rapunzel escapes, finds her lover and restores his sight with herbs, or in some versions, her tears.

What did the witch give rapunzel mother in exchange of a baby?

Cause the witch is evil and she is well jealous and mad at her farther cause of the stealing flowers sort of thing