A High Court judge has raised concerns about "desperate childless parents" being caught up in "strange" baby-selling scams in Africa.
Mr Justice Coleridge said there was evidence that women were going to Nigeria seeking fertility treatment then being sold unwanted babies "for very substantial sums of money" after fraudsters had tricked them into thinking they had become pregnant and given birth.
He said there was more than one case "featuring almost identical facts" before English courts, described the situation as "very serious" and questioned the "lack of involvement" of Nigerian authorities.
The judge raised concerns after giving journalists permission to report details of one case aired before him in the Family Division of the High Court.
Mr Justice Coleridge said the case - involving a Nigerian couple from London - was "very worrying" and gave rise to "very real public interest".
And, at a hearing in London, he agreed to release parts of a written ruling he had made on the case to reporters.
"I am entirely unsurprised by the media interest," said Mr Justice Coleridge, at the hearing. "This is a very serious situation."
The judge added: "It is not the only case, on almost identical facts, before the courts at the moment. It certainly gives rise to very real public interest, particularly the lack of involvement by the Nigerian authorities."
He went on: "The circumstances in this case are completely unusual, very bizarre and truly worrying."
In his written ruling, the judge said the couple involved were members of a charismatic church and had a "strong faith and belief in the power of prayer".
He said the woman was "immersed in a Christian religious environment where miracles are not regarded as impossible".
"All the mother's actions, in my judgment, both in this country and Nigeria, are consistent with her evidence that she had no idea she was involved in this strange scam, designed to put together unwanted children with desperate, childless parents. Her complete desolation when confronted with the reality, as attested to by ... the police ... supports her credibility," he said.
"I am totally satisfied on an examination of all the evidence that this mother had no idea she was taking part in bogus fertility treatment, much less an elaborate and well-tried system for selling unwanted babies to desperate parents in exchange for very substantial sums of money.
He added: "Both she and her husband were hoodwinked and are innocent victims so far as their involvement in these matters is concerned. They neither knowingly participated in the wrongful removal of the child from her natural mother nor in the wrongful importation of her into this country.
"The highest it can be put, as I find it, is that the mother unwittingly took part in an unorthodox adoption process surrounded by an elaborate piece of play acting."
Mr Justice Coleridge said local authority social workers had argued that the woman's version of events was unbelievable.
A lawyer representing social workers had made submissions which included the frequent use of "incredible, implausible, far-fetched and highly improbable".
"The local authority's case is quite simple," said the judge.
"They say it is simply unbelievable that the mother could have gone through this process without at some point appreciating what was going on, especially as in England she had received clear medical confirmation that she was not pregnant. I should be very slow, they urge, to swallow this story."
But the judge said he had concluded that the woman and her husband had been "hoodwinked".
He said he had been shown evidence gathered by an investigative journalist in Nigeria and a September 2011 report from the Port Harcourt Vanguard newspaper, headlined: "Baby Factories: how pregnancies/deliveries are framed".
The report said maternity homes used "illicit means" to procure babies for childless couples for "huge amounts of money".
It said clinics administered substances that "form a sort of tumour in the womb" making women think that they were pregnant.
Another substance was administered to give a "false impression of labour" and a "baby is then sneaked in and made to cry", the report added.
"There are a number of case studies set out in the course of that lengthy, double-page article," added Mr Justice Coleridge.
"Having seen that article, there cannot be any doubt at all that this far-fetched story is rooted most solidly in reality and that this kind of practice is common in certain parts of Nigeria."
Mr Justice Coleridge said the baby the woman brought back from Nigeria had initially been taken into foster care.
But he said he had agreed that the little girl could now live with the woman and her husband.
He added that the couple would be the child's guardians.
"The most important thing is to get the child settled into her final home," said the judge.
"She has no connections to anybody in this country as far as we can tell, or indeed to anybody in the world."
The judge said the woman and her husband were a "charming" couple who had been together for nearly 20 years.
He said he had been "very impressed" with them and was satisfied that they could provide the little girl with a stable home.