In its first-ever ruling on ¡°maternity harassment,¡± the Supreme Court on Thursday nullified a lower court¡¯s decision to dismiss a physical therapist¡¯s claim that she was unjustly demoted on account of her pregnancy.

The term maternity harassment refers to various forms of workplace bullying involving pregnancy, which activists say remains a potent threat to women in Japan¡¯s male-dominated corporate world.

¡°The demotion caused a significantly negative impact on the plaintiff, who forfeited not only her managerial post but financial allowances¡± for which she was previously qualified, presiding Justice Ryuko Sakurai said in the ruling.

¡°Dismissing or similarly maltreating women solely for reasons such as pregnancy, childbirth or taking maternity leave is illegal, and such decisions must be invalidated,¡± she said.

The ruling will force the Hiroshima High Court to re-examine the woman¡¯s claim, and analysts say it is highly likely she will win her case.

The physical therapist was suing her employer for about ?1.7 million in damages. She argues that she was unjustly removed from a managerial position in 2009 after she took a year of maternity leave.

This took place after she made a request a year before, when she learned of her pregnancy, to be transferred to a less physically demanding department. It was her second pregnancy.

The Supreme Court decision also faulted the hospital for not sufficiently explaining to the woman beforehand how her transfer would affect her, especially in terms of salary.

Therefore, she did not consent to the demotion in advance, as claimed by the hospital, it said.

Under the Equal Employment Opportunity Act for Men and Women, employers are obliged to assign pregnant employees to less demanding jobs if they so desire, and are prohibited from maltreatment solely based on such requests.

The plaintiff, who has asked not to have her name publicized, saw her claim dismissed twice, at the district and high-court levels. Both determined that the hospital¡¯s decision was allowable under its power to handle personnel matters.

The hospital reportedly demoted her because the department that she was moved to did not have a corresponding managerial position. It said the arrangement was made with her consent.

In a hearing at the Supreme Court last month, her lawyer reportedly argued that demoting pregnant women during personnel transfers will discourage female workers from giving birth.

Maternity harassment, or ¡°matahara¡± as it is often referred to in Japanese, surfaces in such forms as hectoring by colleagues, and demotions or pressure to quit by employers.

¡°I really hope the ruling today will act as a deterrent against maternity harassment in the future,¡± said Sayaka Osakabe, head of a group called Matahara Net, which supports pregnant women in the workforce.