All kinds of ways to get it...disruption in normal vaginal flora due to too much moisture, not showering enough, antibiotics is a major cause. Some people are just more prone to them than others. It is usually not caused by sex unless the man is uncircumcised. In other words it is usually not sexually transmitted because the yeast has no where to live on a circumcised penis. However it can be caused sometimes by starting sex with a new partner just do to the disruption in vaginal flora. Some women get them every time they have a period or a new sex partner.