Pregnant women are being sacked, demoted or bullied in the workplace despite laws prohibiting discrimination, a Victorian study shows.

Monash University researchers analysed calls from Victorians to employment rights service JobWatch between 2019 and 2020.

They found about 14 per cent of calls were about pregnancy and breastfeeding discrimination complaints.

Those complaints included pregnant women being blocked from taking parental leave, denied days off for medical appointments, and given reduced hours.

"It's happening to women at all stages of their careers and in all industries," lead author Associate Professor Dominique Allen told AAP.

"It's happening when women knew what their rights were and they weren't able to give effect to those rights.

"They were going in saying you need to accommodate this and employers weren't, so women were having to just put up with it."

In one of the report's case studies, a woman shared how she was made to do tasks her doctor said would be unsafe because her employer dismissed the advice.

One new mum was sacked several months into her 12 months' unpaid parental leave, while another woman was offered a demotion with less pay after returning to work.

It is illegal for pregnant women to be treated differently in the workplace but Prof Allen said there were issues with the law.

"There's no impetus or obligation on the employer to do something," Prof Allen said. "They can unfortunately just ignore these things.

"If there was an obligation, what we call a positive duty, on the employer to do something to address discrimination before it happens ... then it wouldn't be just up to the woman to come forward."

Many women do not know what their rights are or are afraid to speak up, JobWatch executive director Zana Bytheway said.

"They don't want to rock the boat with their employment," Ms Bytheway told AAP.

"Those that want to speak out face the daunting prospect of making a discrimination claim.

"That's time consuming, it's costly. Sometimes the outcome is uncertain. And they'll be contemplating this during the busiest time of their lives."

While the latest research focuses on Victorian cases, Ms Bytheway said pregnancy discrimination was common across the country so reforms need to be national.

Currently in Victoria, women have 12 months to make a formal discrimination complaint but Ms Bytheway said that time frame should be increased to two years.

"Their mental health can be negatively impacted, they may feel victimised or lack awareness about their legal rights and protections," she said.

"Combined with the lack of time associated with the general life upheaval of pregnancy, childbirth and parenting, it just makes good sense for these time limits to be extended."

Confidentiality clauses in settlements should also be done away with, Ms Bytheway said.

"Often it means that the perpetrators, the employer, face no real consequences because no one other than her will know," Ms Bytheway said.

"Confidentiality clauses serve to mask endemic culture issues in the workplace."