You know you have a yeast infection because the fungus comes along with its four best friends - redness, discharge (usually white and cottage cheesy), itching, and irritation. Though yeast infections are uncomfortable, they're not considered a serious health threat. Anti-fungal medications can help; topical medication can be messy, so talk to your doctor about oral treatments for use after the first trimester.
The most common signs of a yeast infection are itching and a thick white discharge. There is an over the counter test for infections that is fairly reliable. I recommend that a patient use a three night over the counter cream and if this does not work then she should seek medical attention.