Ambulance Victoria is reviewing why a woman who plummeted three-metres into a sinkhole and later suffered a heart blockage was not taken to hospital.

The 45-year-old woman fell about three metres into a pool of water in a Springvale backyard as she hung out washing yesterday.

She was forced to tread water for about 20 minutes before emergency services workers rescued her.

Paramedics treated her at scene and, at the time, said she was not injured.

The woman who fell into the sinkhole had to tread water to stay afloat while underground. ( ABC News )

The woman's daughter, Rebecca Beaumont, told Fairfax Radio her mother collapsed hours after paramedics left and was later taken to hospital.

"She's got a complete heart blockage now and her heart has weakened from the whole situation," she said.

"This is caused by stress and the fact she was submerged for so long."

Ms Beaumont said she was concerned about how paramedics made the initial assesment of her mother.

"I do find it quite strange, as do the staff at the hospital and the second lot of paramedics that came to the house to take her, that she wasn't taken to hospital."

Ambulance Victoria Group Manager Andrew Watson said the paramedics response was being reviewed.

"It is standard procedure that we conduct a clinical review into a case if someone isn't taken to hospital, and paramedics are subsequently called back within 24 hours," he said.

"That review is being undertaken. Ambulance Victoria is willing to meet with the woman involved to discuss the findings when the review is completed."