"There's over a million orphans in Malawi, and in my opinion the laws need to change because these children need to be rescued," the Material Mom said Thursday on Letterman's "Late Show" on CBS.
Madonna, 48, said she had been warned that pursuing an adoption from the country could be difficult.
"My social worker ... said, 'Good luck. You're going to be making it up as you go along,"' the pop star recalled, according to a show transcript released Thursday evening. "She didn't say don't do it, but she just said expect challenges, and, boy, did we get them."
Madonna and her husband, movie director Guy Ritchie, 38, have been allowed to take 1-year-old David Banda to their home in London. She has two other children, Lourdes, 9, and Rocco, 6.
Yohane Banda surrendered his son to an orphanage after his wife died last year. The couple's two other sons died in infancy from malaria. Banda has said he wants David to stay with Madonna and Ritchie.
Human rights groups in Malawi have said they are concerned the government cut legal corners to fast-track the adoption and they want adoption laws there clarified. A November court ruling allowed a coalition of rights groups to monitor the process. reports AP.
On the show Thursday, Letterman expressed support for the adoption.
"I found it a little upsetting that there was such a tumult and furor over this when in fact the net result was here we have a human being that now has a life," he said.