"I'm angry. I'm 100 per cent sure it wasn't pre-existing," Ms De Luen said.
The healthcare assistant contested the decision through the Disputes Resolution Service but it was upheld, so Ms De Luen has lodged an appeal in the district court.
Labour's spokeswoman for women's affairs, Sue Moroney, believed the decision was gender discrimination.
"It seems just fundamentally wrong that they can suggest that any woman who has had childbirth is walking around with this pre-existing condition," she said.
But in the DHB's case to the Disputes Resolution Service, WorkAon consulted three specialists who all agreed the event precipitated the prolapse. They noted Ms De Luen had predisposing factors including childbirth and a hysterectomy which can cause a weakened pelvic floor heavy lifting would aggravate.
After an internal review in 2011, ACC admitted it had been rejecting too many elective surgery claims since the introduction of a harder-nosed approach in 2008 designed to save money. Last year, following hundreds of complaints to the Herald from disgruntled claimants whose surgery was declined because of "pre-existing" or "degenerative" conditions, ACC said the approach was fair and necessary to avoid a blow-out in levies.
An ACC spokeswoman said it was not involved in the decision to decline Ms De Luen's claim. She said Waikato DHB was an accredited employer which meant it was responsible for its employees' work injury claims in return for a reduction in levies.
Waikato DHB spokeswoman Mary Anne Gill said the DHB could not comment on the case because it was before the district court. However, she said, Ms Moroney's claim of gender discrimination was "ridiculous".
WorkAon said it only acted as an administrator for employers on individual claims.
Turned down
Claims rejected because of "pre-existing'' conditions
* Paul Scotting, 39, twisted his left ankle walking down a grass bank. He was told the injury was the result of old injuries to his other ankle and knee. The decision was overturned by the Disputes Tribunal.
* Lauren Williams, 23, tore her knee cartilage at netball but the injury was labelled "degenerative'' because she had fallen once when she was 12.
* Madeleine Flannagan, 37, suffered a herniated disc in her neck after a car crash. She was told the pain was the result of "degeneration''.