The Northern Territory Government sought advice from doctors about performing an abortion on a teenager in their care, without her knowledge.

The girl, who has a cognitive impairment, became pregnant while at a government-run secure facility in Darwin, Yirra House.

Assessments of the teenager's exact cognitive age, which authorities use to make decisions about her care, vary widely.

The Department of Children and Families sought advice last December, including a possible application to the Supreme Court, to terminate the girl's pregnancy.

However, the girl turned 18 this month and has told friends she is delighted to be pregnant and wants to keep the baby.

Sources have told the ABC doctors and medical staff refused to perform any abortion and advised the department they did not believe it was in the girl's best interests.

After receiving this advice the department dropped its attempts to proceed with the termination.

Community social worker David Cole knows the teenage girl.

"I'm aware through the community that she is pregnant, and it's also been brought to my attention that the department was trying to get her to have an abortion," Mr Cole said.

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"Her journey's been tough and nothing's been easy for her.

"This young girl needs a lot of support. She needs support not only for herself but for this child.

"It would be nice if that support was provided and she was given the chance to actually try and be a good mother and break that pain cycle for this child."

The identity of the baby's father is not known.

Girl 'has the right' to decide on abortion

Mr Cole agreed the girl's cognitive impairment played a role in the department's attempts to end her pregnancy, but said that decision should only be made by the teenager herself.

"Arguing and her rights are two different things. She is [now] 18 and she has the right to make that decision that she wants to or doesn't want to have that child," he said.

"The fact that she has been failed by the system for quite a long period of time and that failure and that negligence has led to the position that she is in today - that's the part that I struggle with."

Department head Anne Bradford released a statement saying the department "is required to make parental decisions for children in care to ensure their physical and emotional safety and wellbeing. Where a decision is particularly significant, i.e. the termination of a pregnancy, the decision is informed by appropriate medical, psychological and legal advice."

Ms Bradford said all decisions by the department were made with the best interests of the child in mind.

Mr Cole said he was worried about what would happen to the girl's baby when it was born later this year.

"I'd imagine that the department will take her child away from her as soon as it's born," he said.

However, the department said it "will not have a role in the child's life unless concerns are raised regarding the mother's capacity to parent the child. If concerns are notified, an assessment will be undertaken to identify any risk to the safety of the child and what actions need to occur to address the risk."

Medical intervention is legally complex, solicitor says

The situation was legally complex, according to Jane Sanders, the principal solicitor for the Shopfront Youth Legal Centre, a free legal service for homeless and disadvantaged youth.

She said under law there were mechanisms for carers of people with cognitive impairments to apply to the court for consent to undertake medical procedures.

"There's different laws in different Australian jurisdictions,'' Ms Sanders said.

"If there's somebody, a person or carer or medical practitioner, who is really concerned the person or young adult needs some kind of medical intervention but doesn't have the capacity to consent in their own right they can apply to the court."

However, she said the court would have to agree to the application.

"In my experience they go to quite significant lengths to determine whether a young person does have capacity to make their own decisions.

"They have to be satisfied the person doesn't have the capacity to consent. They also have to look at what's in their best interests.''

Ms Sanders said such situations did occur from time to time but more often related to applications for sterilisation of people with intellectual disabilities or transgender issues.