A woman who was held in detention on Nauru before giving birth to a son in Darwin last year after complications during the pregnancy has described today's High Court decision as a nightmare.

"It's like dying," the woman, who now faces a return to Nauru, told 7.30.

"It's waiting for dying."

Immigration Minister Peter Dutton signalled his intention to send a group of 160 adults, 37 babies and 54 children in Australia back to Nauru, a regime the High Court has ruled is constitutionally valid.

The woman acknowledged she and her husband arrived by boat, but she said the rules were changed after they had left their home country.

"We didn't know the law has changed in between," she said.

"But that has no bearing on our kids."

Her son Samuel is one of the 37 children born to asylum seeker parents in Australia who could be flown offshore because of the ruling.

"Our kids are innocent," she said.

"Like any father and mother we have wishes for our kids and this is my first child.

"I believe, and the mothers in my situation believe, that their kids are Australian."

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PM vows 'to keep our borders secure'

Paediatrician Dr Josh Francis, who treats children in detention in Darwin, including many of whom have also been in detention on Nauru, has defied the threat of going to jail to speak out about the treatment of children in detention.

Paediatrician Dr Josh Francis said children have experienced trauma from their time on Nauru. ( ABC News )

"Some of the kids who we will see are actually babies who are born in Australia and all they know is the security of their parents," he told 7.30.

"If the safeness and security of their parents is taken away, you have a mother who is depressed, you have a father who is absent because he can't cope with the thought of dealing with the family through all this — those sort of things have a massive impact on even the youngest children.

"But it's the older ones, the older ones who have experienced trauma on Nauru, who have seen people trying to starve themselves, have seen people trying to hang themselves, have seen the stress and depression that occurs among the adults they live amongst in Nauru.

"And so for many of them what they're terrified of is what goes on all around them and they know that it's worse in Nauru than it is here in Australia."

Prime Minister Malcolm Turnbull has in the past declared his discomfort with Australia's refugee policies but has maintained the tough line of his predecessors.

"Nobody should ever doubt the resolve of this Government to keep our borders secure, to prevent the people smuggling racket, to break their business model and keep lives safe, to prevent drownings at sea and to protect vulnerable people," he told Parliament.

His Government now faces two big decisions which could risk an outcry either way — whether to send the children to Nauru and whether to pursue the doctors for speaking out.