A pregnant woman has been spotted walking beside a bus near Darwin's Wickham Point Detention Centre, where a stand-off has been underway between between guards and two Iranian families protesting against being housed in the facility.

There has been no confirmation as to whether the woman spotted in the video - taken from a helicopter - was one of the heavily pregnant women who has been in the bus since Saturday.

It is understood that while in immigration detention in Nauru, authorities already determined that the women and their husbands were refugees, and the Australian Government told the women they would be taken to Australia to give birth.

They have been refusing to go to the immigration detention centre since they arrived by bus late on Saturday night, according to the Darwin Asylum Seeker Support and Advocacy Network.

Earlier, a 10-year-old refugee involved in the protest was believed to have left the bus involved.

The Refugee Action Coalition has named one of the women as Maryam, who they say was on the bus with her husband Adnan and 10-year-old son Amir.

The Darwin Asylum Seeker Support and Advocacy Network has told the ABC Amir is now off the bus and believed to be in the Bladin detention centre nearby.

Another pregnant woman, Tahere, was believed to be on the bus with her husband Hossein.

Soliman Sharvani, a brother of one of the men on the bus, said he was worried about the women's health.

This photo shows two Iranian refugees named Adnan and Maryam boarding a plane in Nauru bound for Darwin, according to the Refugee Action Coalition. ( Supplied: Refugee Action Coalition )

"I'm way worried about my brother wife, she's pregnant," he said.

"It's the last month for her pregnancy, I think it's too dangerous in Darwin on a bus in that weather for a pregnant woman."

A spokesman for Immigration Minister Scott Morrison said the Department and the detention service provider are working with the families to resolve the situation.

The spokesman said the Minister denies the group were told they would be placed in the community when they came to Australia.

Treatment of pregnant women disgraceful: refugee advocate

Refugee Action Coalition spokesman Ian Rintoul has told 105.7 ABC Darwin the women had been found to be legitimate refugees and should not be put into detention.

"They're both eight months pregnant, it is just ridiculous," he said.

"The people themselves offered to pay for a motel room last night.

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"For the cost of a motel room the department's left them on the bus. It beggars belief."

The women were sent to Australia to give birth, which the refugee advocate said was standard practice.

One of the women has had some medical problems during her pregnancy, he said.

"For them to say they would rather go back to Nauru and take whatever risks might be associated with having the babies on Nauru rather than spend a night in detention, it just says a lot about what they have been through in detention on Nauru," he said.

He said having been found refugees should mean they had the right to live in the community while in Australia.

"There doesn't seem to be any possible justification for placing them in detention and depriving them of their liberty," he said.

Mr Rintoul said his organisation had engaged a lawyer to represent the refugees.

The executive director of the Refugee and Immigration Legal Centre in Melbourne, David Mann, said the women had sought legal help from the centre.

Birthing groups call for action from NT minister

Two childbirth associations have called on the NT Health Minister to intervene in the protest.

The Childbirth Education Association and Darwin Homebirth Group have called on Minister Robyn Lambley to ensure the two pregnant women are put into housing in the community.

They said that would ensure the best possible outcome for both the mothers and the infants.

Childbirth Education Association president Leisa Masters said she did not want to hear that it was a federal issue.

"These women are here in our community, to use our services," she said.

"We are morally responsible to deliver care most appropriate to ensure the health and safety of mothers and babies.

"The severe stress that these women are currently under is not conducive to this."

Darwin Home Birth Group president Alison Sharma said the homebirth community was also absolutely clear that these women needed to be housed in the community.

"We are not interested in the semantic word games of Federal Minister Scott Morrison," she said.

"The severe stress that these women are under will affect both their birthing and potentially the long term health of the children.

"It is unthinkable that two heavily pregnant women feel forced to sit on a bus with an absolute lack of facilities in the current heat conditions and we call on Robyn Lambley to act."

A spokesperson for Ms Lambley said the issue was one for the Federal Government.