Workers with certain health issues could be given 12 more days off part of a push to expand reproductive leave to all Australian employees.

Hundreds of workers at disability service provider Scope will be the first in Australia to receive 12 days of leave for severe menstrual pain, endometriosis, IVF, vasectomies, menopause, gender transitioning therapies and other health issues.

The Health Services Union is calling for the entitlement to be extended to all Australian workers.

The union's national senior assistant secretary Kate Marshall received fertility treatment to conceive her twin daughters after two miscarriages.

For her and many other women, reproductive leave would have been life-changing.

"I did want to work but I also desperately wanted to have a family - why should a person have to pick one or the other?" she said on Monday.

"It shouldn't be down to being lucky enough to have an understanding boss.

"All workers deserve this critical leave."

Workers, especially women, were burning through their leave to look after their reproductive health, Ms Marshall said.

This extra 12 days of leave could allow women to stay in the workforce for longer, accrue more superannuation and help close the gender pay gap.

Contraception, hormone therapy, hysterectomy, menstruation, miscarriage, pregnancy, poly-cystic ovarian syndrome, screenings for breast and prostate cancer would also be covered under reproductive leave.