Key Points:

A Dunedin mother has been sentenced to intensive supervision and community work for causing the death of her 22-month-old twin daughter, who choked to death after being assaulted this year.

The details of the incident were made public for the first time yesterday when the 27-year-old woman was sentenced in the High Court at Dunedin.

She was originally charged with murder but that charge was withdrawn and replaced with the comparatively rare charge of infanticide after two psychiatrists found the balance of the woman's mind was disturbed by depression at the time she caused the child's death. She pleaded guilty.

The dark-haired, slightly built woman was in tears as Justice Graham Panckhurst recounted the events of May 26 when her two oldest children were at school and she was at home with her youngest son and the "unwanted" and prematurely born twin girls. At the time, she was effectively a solo parent and "to put it mildly, wasn't coping", the judge said.

Because the twins spent seven weeks in the neonatal intensive care unit after their birth at 33 weeks, there were problems with bonding, in particular with the younger.

The woman's depression and low mood grew, she became progressively more overwhelmed with the demands of caring for five children and her irritability and anger focused on the younger twin.

On May 26 the woman banged the child's head against a couch several times. When paramedics arrived she was dead.

A post-mortem examination found evidence of past injuries including a fractured rib and a fractured vertebra in the lower back area, the judge said.

He ordered her name to be suppressed.