Police Hail Man A Hero For Saving Pregnant Woman From 'Unprovoked' Attack

A man said he was acting on "instinct" when he stepped in to save a heavily pregnant woman from a "vicious" and unprovoked attack.

The alleged victim, who is 30 weeks pregnant, was walking along Wentworth Avenue in Surry Hills just before 9am on Tuesday.

NSW Police allege a 28-year-old woman emerged from an alcove and -- without provocation -- repeatedly punched her in the head.

"The assailant allegedly pulled the victim’s hair and rammed her into a power pole," police said.

Martin Barrett was walking to work at the time and quickly jumped to the young woman's rescue, wrestling her away from the alleged attacker.

READ MORE: Pregnant Woman Bashed, Thrown Into Pole In Unprovoked Attack

Martin Barrett.

Barrett -- who moved from London to Sydney seven years ago -- said he acted on "basic instinct" and wasn't concerned for his safety while trying to separate the women.

"I could tell it was one-sided," he told reporters on Wednesday.

"It wasn't a fight, it was an attack and at that point I realised this person was defenceless and just tried to help as any decent human would."

CCTV shows an assault on a pregnant woman in Sydney. Photo: NSW Police

Detective Superintendent Gavin Wood said Barrett's decision to take action during the "significant and despicable assault" needed to be recognised.

"The person next to me is a hero. That term we don't use lightly," he said, standing next to Barrett.

"It was a great deed, I know it's recognised and appreciated by the female victim, who as we all know was 30 weeks pregnant, and her husband. They've asked me to say that to everyone that they are so appreciative of what this man has done."

Barrett said the hero accolade "might be over-doing it" and expected the same behaviour of other "decent" people.

The alleged attacker, a Mount Druitt woman, was pulled away by a second man and arrested by an off-duty police officer who had been walking past at the time.

Dramatic CCTV footage captured the incident, showing Barrett lead the pregnant women to safety while her alleged attacker pointed and yelled.

"Looking back at the visuals it's pretty disturbing," he said.

"But I guess its one of those things, life throws you curve balls and you've got to try deal with them as best you can and I'm just glad that the baby and mother [are] doing okay."

The English man said he did not realise the woman was pregnant until after he intervened, when she began clutching her stomach and crying.

She has since been released from hospital with minor injuries, Wood said, and her unborn baby is unharmed.