Miss France and Miss Belgium have joined a growing list of the world's beauty queens who have said they will not be going to Nigeria.
Amina Lawal, 30, is due to be stoned to death after giving birth outside marriage. In August, her appeal was rejected by a Sharia court.
The contest will be held in Nigeria this year after Nigerian Agbani Darego became the first black African woman to be crowned Miss World in 2001.
It is also under threat from militant Islamic groups in Nigeria, which call it a "parade of nudity" bound to promote promiscuity and HIV/Aids.
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"The Miss France committee is joining the protests against Nigeria, which condemns women to death for adultery. These sentences are barbaric and unacceptable," said Genevieve de Fontenay, head of the Miss France committee.
"I have decided not to take part if Amina Lawal is not freed," Miss Belgium Ann van Elsen told Le Soir newspaper.
Contestants from Denmark, Ivory Coast, Kenya, Norway and Togo have already announced that they will not go to Nigeria unless the death sentence on Ms Lawal is dropped.
However Miss Sweden, Sophia Hedmark, will be using the platform in Nigeria to protest against the harsh Sharia punishments.
''There is nothing to be gained by not going to Nigeria... but I plan to protest against the ruling in interviews with journalists," she said.
This is a policy backed by Jide Asumah, one of the organisers of Miss World in Nigeria.
"If they don't come they have no way of making their voice heard. By coming to Nigeria they will make their position known, which will have a better effect," he told the French news agency, AFP.
The Polish Miss World committee said it was concerned about the safety of its representative after the Islamic group, Jama'atul Muslimin, branded the contest ''an abomination'' and others threatened to disrupt it.
Ms Lawal's lawyers say they will appeal against the death sentence, which the Nigerian Government has also condemned.
A similar sentence passed on another woman, Safiya Husaini, was overturned on appeal just as Ms Lawal was being convicted earlier this year after a vigorous campaign by international human rights groups.