Madonna is due to arrive in Malawi on Sunday to begin the process of adopting a second child from the country.
The pop star wants to adopt a young girl called Mercy James, local officials have said.
The girl is in the same orphanage that was home to David Banda – the boy Madonna took to live with her in the UK when he was 13 months old.
But the singer has come in for criticism from the Save the Children charity, which urged her to reconsider.
Madonna is due to sign adoption papers with Mercy James’ uncle in court in the capital Lilongwe on Monday, the Associated Press (AP) news agency reported.
An unnamed welfare official told AP the girl’s mother was an unmarried 18-year-old who died a few months after the baby was born.
There are differing reports of Mercy James’ age, with AP saying she is four years old and Agence France Presse (AFP) saying she is three.
Save the Children spokesman David Nutt told BBC News the British-based charity wanted Madonna to think again.
“We don’t want to pick on one individual – any time, any set of circumstances can change,” he said.
“But the problem is, very often this is the wrong thing to do, and Madonna tends to make it seem like it’s the answer to everything and all problems, and it just isn’t.”
But Steven Whitehead from the charity Oasis, which represents families who adopt from abroad, said foreign adoption was a good idea in many cases.
He said: “There are a number of children for whom inter-country adoption represents their only chance of having a family, and the human convention on the right of the child gives every child the right to a family.
“And it’s much better for them be in a family, wherever it may happen to be, than be in institutional care. The damaging effect of institutional care on children is so well recognised that, you know, it’s just not an issue of debate.”
Madonna’s spokeswomen, Liz Rosenberg and Barbara Charone, and her lawyer in Malawi, Alan Chinula, have not commented.
Writing in response to e-mailed questions from Nation readers last week, Madonna said: “Many people – especially our Malawian friends – say that David should have a Malawian brother or sister.
“It’s something I have been considering.”
In 2006, critics accused the Malawian government of sidestepping laws banning foreign adoptions in order to allow the celebrity to take David home with her.
Madonna’s adoption of David Banda was confirmed last year.
‘Role model’
After the adoption was legalised, Madonna said the difficulties had arisen because “this adoption essentially was the beginning of the creation of adoption laws in Malawi”.
She hoped it would make it easier for others to adopt from the country and explained: “I am the template or the role model, so to speak, for future adoptions.”
The star also has two biological children – Rocco, her son with former husband Guy Ritchie, and Lourdes, whose father is Carlos Leon.
Film director Ritchie and Madonna’s divorce was finalised in November.
Malawi does not, as a rule, approve adoptions for single or divorced people, but the official at the country’s welfare department said that each case was considered on merit.
Madonna has also established a charity, Raising Malawi, which aims to provide accommodation, food, education and other support to orphans in the country.