HE SHOOK his eight week old son, then threw him on a bed, leaving him with bleeding on the brain.

But the 38-year-old Maryborough man responsible won't spend a day behind bars after he was released on immediate parole.

The man, who cannot be identified for legal reasons, pleaded guilty in Maryborough District Court to assaulting the baby and the baby's mother.

The court heard the couple's relationship had broken down but he remained living in the same home as the woman's carer.

She was said to have had a number of health issues including epilepsy and bipolar disorder.

Both took care of the baby.

The court heard the man had been at a speedway event at Kingaroy the night before the attack.

The baby's mother woke him about 4.30am to check on the baby while she prepared to feed him.

The man picked the baby up and told him to "shut up".

He then shook the baby three or four times and threw him on the bed.

The baby immediately stopped crying and went limp. His eyes were open but he was struggling to breathe.

The court heard the man told her he was sick of waking up early and he pushed her, causing her to fall forwards.

She picked up the baby and asked the man to call and ambulance, but he refused, telling the woman she was not taking the baby anywhere.

The court heard the woman took the baby to the defendant's parents' house.

A nurse attended to the baby during a scheduled home visit later that day and noticed twitching of his arms and legs.

The baby was taken to Hervey Bay Hospital and later transferred to Brisbane where further tests revealed cranial subdural haemorrhages and small areas of hemotoma.

The baby was also suffering seizures and had to be medicated.

When the man was later interviewed by police, he told them the woman had prepared a bottle and became upset because she thought he had dropped the baby.

He denied shaking the baby and throwing him on the bed or pushing the woman.

He accepted he refused to call an ambulance, but said that was because it was windy and raining and he didn't want to take the baby out in those conditions.

The court heard the baby had been taken into foster care since the incident and remained there due to his mother's health issues.

It also heard injuries the baby suffered had not had permanent consequences and the offending wasn't prolonged.

The man was said to have a "significant intellectual impairment" and was supported in court by his father.

Judge David Reid said the attack had been made on a "very vulnerable, defenceless eight week old baby".

But he accepted that it was a "tinderbox" situation, with the stress of caring for the woman and a newborn baby, as well as the man's intellectual impairment, leading to the situation.

The man was sentenced to two years in prison, but was released immediately on parole.