A pregnant Rohingyan couple seeking asylum in Australia but transported to Nauru say the conditions are so bad there that they decided to get an abortion.

The father says he and his wife made the decision to terminate the pregnancy because of the heat in the camp, the long waits for food and the poor state of facilities such as toilets.

Immigration Minister Scott Morrison, however, has denied that the conditions were to blame and labelled the claim "outrageous".

Mamun Motiur, 24, says he and his wife, Salima, met in Indonesia while on their way to Australia.

They arrived on Christmas Island in early December and within days were transferred to Nauru.

Mr Motiur said it was there that they discovered Salima was pregnant and decided to seek an abortion.

"In Nauru, the weather is very hot - up to 40 degrees," Mr Motiur said.

"And if we born with a child in Nauru the child must die because the facilities [are] not good in there.

"There is a very small room. Families are given a fan. But in a single camp there is no fan. When you take meals – lunch and dinner – you must be standing two hours in the line.

"So we think if we (have) the child now he, the child, has no future. So we decided to take abortion."

Couple flown to Brisbane with wife six weeks pregnant

Mr Motiur says he expressed their concerns to immigration officials and later raised the prospect of an abortion with the medical service provider IHMS.

The criminal code of Nauru makes abortion an offence.

The couple's lawyer, Mark Johnson, says Salima was about six weeks pregnant when the couple was flown to Brisbane.

"Salima has described what occurred shortly after they got there," Mr Johnson said.

"She was given some medication, some tablets and then the following day some more tablets and it seems that those tablets brought on a spontaneous termination of her pregnancy."

In a statement, Mr Morrison said privacy laws prevented discussion of specific cases but released a statement.

"Primary health care for pregnant women is assessed on a case-by-case basis and a care plan is developed appropriately," he said.

"Such decisions are private and personal and are taken in consultation with their doctor for their own reasons, and is a matter for them.

"When deemed necessary, transferees are moved to Australia temporarily for medical treatment."

Ian Rintoul, from the Refugee Action Coalition, says it was a deeply concerning case.

"I think they have recognised at the very least the extreme psychological trauma that Nauru has inflicted on Salima and the impossibility in her mind of being able to go ahead with having a baby in the conditions on Nauru," Mr Rintoul said.

He says pregnant women should not be held in offshore detention centres, but the Minister denies the conditions were to blame.

"The Government rejects any suggestion that Australia's offshore processing policy provides any legitimate medical grounds for a parent to choose to have an abortion," Mr Morrison's statement said.

"This is yet another outrageous claim."

Mr Johnson said the couple is now in detention in Darwin.

"I have briefly spoken with the psychiatrist who examined her last Wednesday and that is in fact since I have last seen her," Mr Johnson said.

"He has described her as 35 kilograms in weight. She's only a slight figure but 35 kilograms anyone would accept as very much underweight. Her health is still not great."

Mr Johnson also said they will take further legal action if the department attempts to return them to Nauru.

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