A teenage father accused of murdering his baby son by biting his nose and violently shaking or swinging him previously injured the child’s mother while she was pregnant by pushing her to the ground, a jury has heard.

The mother, who is accused of child cruelty, sustained facial injuries in the alleged attack by her partner, Winchester crown court was told.

Both the father, who was 16 at the time of the baby’s death, and the mother, who was 18, deny the charges against them. Neither can be named.

The jury has been told that neighbours heard a “bloodcurdling scream” as the six-week-old baby was allegedly attacked by his father. The child sustained a skull fracture, a broken leg and rib fractures.

Opening the case on Tuesday, Adam Feest QC, prosecuting, said the attack took place at the mother’s studio flat in Southampton in February after the couple had spent the evening at a neighbour’s home, during which they were seen drinking vodka and beer.

Feest said: “He [the child] met with a violent end as a result of an assault or assaults perpetrated against him in a small flat where he was with his father and mother. Residents across the road recall hearing what they described as a bloodcurdling or painful scream coming from the flat at about 3am.”

Feest said after the baby was taken to hospital, the father told a neighbour: “What have I done?”

The prosecutor continued: “The explanation he gave police was his son had accidentally fallen from the sofa when having his nappy changed, or fallen from his arms when he and [the mother] were arguing.

“This cannot account for the severity and multiplicity of the injuries sustained. The injuries taken together are in keeping with a violent shaking or swinging, or indeed both.”

He said a bite mark on the baby’s nose matched the father’s dental prints.

Feest said the mother, now 19, said she had not sought help because she did not want to lose her son or partner. “It may be she helped clear up the injury that [the father’s] bite caused,” he said.

The mother is on trial for child cruelty for failing to protect her baby or seek help for him.

On Wednesday, the mother’s sister told the court that the mother, while pregnant, was pushed to the ground by her partner.

The sister said: “She said he pushed her with some force and she fell to the floor.” The mother suffered grazes to her face but forgave her partner.

The sister said she and her own partner visited the defendants on the evening before the baby died and said the child was “asleep and calm”. She said: “Everyone was calm, happy. He was asleep the whole time I was there.”

The sister said the mother was pleased to have had a baby, and added: “It was like she was born to be a mum.” She said the death of the child had affected the whole family. “It destroyed us,” she said.

The trial continues.