Later that week, she sought leave so she could undergo a medical procedure.
After she returned, Mr Ong called her into a meeting where he read a letter terminating her employment.
It cited the amount of sick leave she had taken as one of the reasons for the dismissal.
A previous employee's unsubstantiated claim that Ms Massie had stolen from a work till was a major factor in her sacking, the ERA ruling said.
Ms Massie told the authority she was greatly upset about the comments in the letter about her taking sick leave.
Her miscarriage had been unplanned and had left her in an extremely distressed and vulnerable emotional state, she said.
Following the meeting with Mr Ong, Ms Massie said she was upset and shaking and had gone to the bathroom to compose herself before returning to her duties.
"Ms Massie said at this point Mrs Ong had approached her, and apologised for having to terminate her employment.
"Ms Massie said she had asked Mrs Ong if her dismissal had been as a result of her becoming pregnant and having a miscarriage, and that Mrs Ong had replied that the pharmacy was a small business and as Ms Massie wished to have a family, she was unsure that that would suit the practice," the ERA ruling said.
ERA member Eleanor Robinson said the dismissal was unjustified and carried out improperly.
She criticised Mr and Mrs Ong for not giving Ms Massie a chance to respond to unfounded accusations she was stealing money in her ruling.
Dismissing Ms Massie just days after her miscarriage compounded her distress, Ms Robinson said.
"Ms Massie is also entitled to compensation for humiliation and distress. I find that in respect of the unjustifiable dismissal, Ms Massie suffered significant distress."
A ruling on costs was reserved.
