The 51-year-old star already has two children from Malawi, son David Banda and daughter Mercy, as well as Rocco, from her marriage to Guy Ritchie, and Lourdes, from a previous relationship.
But the singer, whose eight-year marriage with film director Ritchie ended last year, has said she could expand her family.
Asked whether she would adopt again, she told GMTV: "Never say never."
The star, who funds the Raising Malawi charity serving 25,000 orphaned children, added: "I'm really proud of the work that I'm doing in Africa. I feel a tremendous sense of accomplishment in terms of my career and the work that I have done.
"I have four children now and I'd like to think I'm a good mother. I feel a great sense of satisfaction in all areas of my life."
Madonna, who has moved back to New York following her split with Ritchie, said she did not miss London pubs.
But the pop queen, whose former husband owns the Punch Bowl pub in London, said: "I miss being able to walk around the neighbourhood. It's more mellow, laid back and relaxed (in London) than it is in Manhattan."
And seems like she felt the need of explaining her fitness obsession:
"(I do it) for health reasons, and for aesthetic reasons. If I have to go out on stage and, you know, jump around in a pair of hot pants I better look good and also when I perform I'm like an athlete and I have to be in good shape. I'm not panicked, I just know what my job is and I know that if I want to be able to wear whatever I want to wear on stage then my body better look good."