According to telegraph.com.au, the agency said more women complained to them of poor treatment because of pregnancy in 2012-13, topping discrimination because of physical or mental disability.
It is the first time pregnancy has formed the majority of complaints.
Workers made 235 complaints to the agency: 28 percent from pregnant women, 21?percent from people with physical or mental disabilities and 11 percent from those who felt their family or career responsibilities resulted in them being treated differently, the report said.
Australian Council of Trade Unions president Ged Kearney said it was concerning, but 'sadly, not a surprise'.
The ACTU pregnancy discrimination hotline had about 500 calls during one 24-hour block.
Complaints included being sacked, passed over for promotion, denied training and receiving inappropriate comments after they revealed they were expecting, the report added.