According to media reports, the incident was reported in on the Shenzhen Airlines flight from Nanjing to Guangzhou last month. This happened despite both bathrooms on the plane being vacant at the time.
When asked why she didn't get the child to use the bathroom instead, the mother answered, "Your bathrooms are too small, three of us can't get in. It's so spacious out here!".
The woman did not extend any apology for her behaviour. Outraged by the woman's attitude, a flight attendant took her case to the Internet.
Many people expressed their disgust at the women's action after the incident was shared on social networking site Weibo.
According to reports, the women were ordered to clear up the mess themselves.
A similar incident was reported last year when a child was allowed to defecate in his seat during a flight from Beijing to Detroit.