The mother of a premature baby has been found guilty of beating the six-month-old so badly she was left with brain damage and broken legs.

Shana Tooman, 28, claimed she was carrying her daughter when she tripped, dropped the child and then fell on top of her at her home in Pakuranga, Auckland, in July 2017.

But she was found guilty of grievous bodily harm with intent to injure on Wednesday after medical experts ruled the baby's injuries were unlikely caused by accident, according to Stuff.

Shana Tooman, 28, claimed she was carrying her daughter when she tripped, dropped the child and then fell on top of her while in her Pakuranga, Auckland, home in July 2017 (stock)

Tooman assaulted the newborn while her other children played in another room in the house, the court heard.

When she noticed the baby struggling to breathe she called her brother, who was living at the back of the property.

Her brother told her to call an ambulance.

Doctors at the hospital found the little girl had skull fractures, bleeding on the brain and severe brain damage.

She also had a broken left leg and a shattered right leg.

Tooman gave two versions of events to police about what happened to her child.

In her initial interview she claimed she went to check on the baby and found her unresponsive.

However she was found guilty of grievous bodily harm with intent to injure on Wednesday after medical experts ruled the baby's injuries were unlikely caused by accident (stock)

In the second interview - almost four months later - she gave a similar version to what she told the court.

She told police she was scared to tell the truth in the first interview.

However Dr Patrick Kelly, the paediatrician caring for the baby, said Tooman's claims couldn't explain the baby's injuries.

Tooman will be sentenced in June.