A New South Wales mother has won a legal battle to breastfeed her 11-month-old baby after the Family Court overturned an injunction that banned her from doing so because she got a tattoo.

The injunction was unanimously thrown out by the Family Court that found the primary judge based his decision on an internet search.

On June 5, the 20-year-old mother was banned by Judge Matthew Myers of the Federal Circuit Court from breastfeeding because she had recently been tattooed.

The concern was that she might transmit a blood-borne disease such as hepatitis or HIV to the infant.

The mother was tested and found not to have either disease but Judge Myers still decided to grant an injunction to stop her breastfeeding her son.

He said there was still an unacceptable risk to the baby because the tests were not conclusive after studying documents from the websites of Hepatitis Australia and the Australian Breastfeeding Association.

On Friday, the full bench of the Family Court unanimously overturned the decision, finding Judge Myers made the order based on evidence that "should not have been relied upon".

'Judges must not mistake their own views for being facts'

Family Court judge Murray Aldridge said Judge Myers' reliance on the documents highlighted the need for expert opinion evidence to be given.

"Judges must not mistake their own views for being either facts not reasonably open to question or as appropriately qualified expert evidence," he said.

"That those views may have been obtained by the judge searching the internet compounds, rather than alleviates, the difficulty."

Justice Aldridge said the evidence "was not capable of establishing the risk identified by the trial judge".

The Family Court also found the injunction by Judge Myers failed to consider the benefits to the baby, both emotionally and physically, of continued breastfeeding and any negative effects of it suddenly stopping.

The judgement said the matter came before Judge Myers earlier in June after the father failed to return the baby to the mother's care.

The baby's father then raised concerns about the mother's tattoo during the bitter parenting dispute.

The full bench of the Family Court also found Judge Myers erred by ordering the baby spend six hours a day on four days of the week with its father.

The court changed this order to two days per week for five hours each day pending the conclusion of another hearing.

AAP/ABC