A woman who pleaded guilty to causing the death of a baby boy by smashing her car into his nursery while drink driving has been sentenced to three years and eight months in jail.

Melissa Ann Waters was charged with driving under the influence of alcohol and dangerous driving causing death after she crashed her utility into a house in the Perth suburb of Merriwa on January 25, ploughing into the room where eight-month-old Nate Troy Dunbar was sleeping.

She was sentenced in the WA District Court on Tuesday and will be eligible for parole after one year and 10 months.

When she pleaded guilty in May, aged 35, Waters said she had caused "unbearable suffering" to Nate's family.

"I will spend the balance of my life in an attempt to atone for the pain and loss I have caused," she said at the time.