About 20 percent of working women have experienced illegal "maternity harassment," or discrimination against pregnant women and mothers in the workplace, a survey by the Japanese Trade Union Confederation (Rengo) has revealed.

The online survey of 1,000 women nationwide aged between 20 and 49 who became pregnant while employed showed Monday that 20.9 percent experienced unfavorable treatment or even outright harassment.

Of the total, 9.8 percent said they were verbally harassed, 7.8 percent reported being fired or not having their contract renewed. A further 3.3 percent said they were demoted or that their assignments were changed against their will.