An Illawarra mother who left her children home alone in a house that later caught fire while she went to visit her new boyfriend in a neighbouring suburb has sobbed in court after being sentenced to six months behind bars.

The woman, who cannot be named for legal reasons, pleaded guilty to three counts of failing to provide for a child causing danger of serious injury, admitting she had put the lives of each child at risk with her selfish decision.

The Illawarra mother sobbed as she was led downstairs to the cells below the courthouse to begin her sentence. Credit:Illawarra Mercury

Court documents said the woman left her 12-year-old daughter in charge of her toddler and four-month old baby boy from about 9pm on March 2, with the intention of not returning to the house until 6am on Monday - some 33 hours later.

The older daughter's attempts to cook her siblings dinner went awry about two hours after her mother left and resulted in a fire breaking out inside the home's kitchen.