Yeast infections are unwelcome no matter what life situation you find yourself in. However, during pregnancy not only are they particularly unpleasant but expecting mothers are particularly prone to developing them. Partners of pregnant women often report noticing a slightly sweeter or “fruity” taste of the vagina when conception is first suspected. This additional glycogen (natural sugar) in the vagina is due to higher levels of the hormone estrogen.
According to several sources, “your higher level of estrogen during pregnancy causes your vagina to produce more glycogen, making it even easier for yeast to grow there. Some researchers think estrogen may also have a direct effect on yeast, causing it to grow faster and stick more easily to the walls of the vagina.” (BabyCenter, 2011) Yeast thrives on sugars, meaning the hormonal changes your body undergoes in order to nurture a fetus also generates a lovely atmosphere for yeast cells.
https://www.empowher.com/pregnancy/content/recipe-relief-preventing-yeast-infections-during-pregnancy