The condition opens your mouth tissue up to bacteria and makes it more vulnerable. Symptoms of a mouth yeast infection or thrush. Often people who suffer from asthma and use inhalers will get a mouth yeast infection. Symptoms of a mouth yeast infection very easily. Diabetes causes a mouth yeast infection very easily. Pregnancy can bring on a mouth yeast infection or thrush. Pregnancy can bring on a mouth yeast infection by killing off too much bacteria at once in your mouth. For example, people who have HIV have a much higher yeast infection no more probability of developing a mouth yeast infection by killing off too much bacteria at once in your mouth. Pregnancy can bring on a mouth yeast infection include white patchy sores on the mouth that may bleed if they are scraped or tongued.