Kevin Wilson kicked and stamped on his ex-girflriend's stomach so hard he killed her unborn baby.
The horrific attack, which took place on a Peckham street in June this year, left 22-year-old Malorie Bantala with three broken fingers as she tried to protect her baby.
Ms Bantala's baby boy was delivered stillborn by emergency C section at 22 weeks gestation.
A court heard how 22-year-old Wilson and his 17 year-old accomplice only stopped when someone 'opened their window to shout at the pair'.
Opening the case at the Old Bailey, prosecutor Jonathan Rees QC said: 'It was a cowardly and callous attack, each male wearing a motorcycle helmet in an apparent effort to conceal his identity.
'One of the attackers was the unborn baby's father - Kevin Wilson. He had made it clear that he didn't want the baby to be born and was not pleased when Miss Bantala informed others that he was the father.
'We say that he took matters into his own hands and decided that he would end the pregnancy by violence.'
Wilson denies taking part in the attack on his ex-girlfriend, telling police he was visiting his brother and a friend on his estate at the time.
The trial continues.