FIRST ON 7: Guns have been pointed at the head of a heavily pregnant woman during a home invasion in Sydney's south-west.

The victim, Zena Al-Achrafe, feared she might lose her baby as the men tore the home's walls apart, looking for money.

Zena was taken to hospital for an examination after the ordeal.

"[The baby] wasn't moving for a while, but now she's okay," Zena said.

The 21-year-old was alone in her unit when the masked men burst in, and stood over her in bed.

"I woke up to two guns pointing at my face, my husband wasn't home, noone was home," Zena said.

She was ordered to the floor while the men ransacked her granny flat, looking for cash they were convinced was hidden in the walls.

"They wanted money from the wall, I told them to break down all the walls take whatever you want, leave me alone, I'm pregnant."

The reign of terror lasted half an hour, with the men threatening to hit Zena if she didn't stop screaming.

When the men failed to find the money, they fled into bushland.

"They threatened to follow me in shopping centres and hospitals if I didn't give them their money back," Zena said.

Police will examine a note left by the men, demanding $40,000 in cash, be delivered to a nearby park, by next week.

"This is the most horrific crime, one of the worst I have come across for a number of years," Superintendent Johnson said.

Family are looking after Zena now, because she is too scared to be alone.