At my last prenatal appointment, one of things mentioned was how vaginal infections can sometimes cause early labor, and that pregnancy makes women more susceptible to vaginal infections. I must admit that I'm rather ignorant on the subject because I've never had an infection, so I asked the doc how to prevent it.
She said that the first thing to do is always wear cotton panties.
She said it's even better to wear a cotton panty-shield as well.
Never douche or wash the vaginal area with antibacterial soap, as this can get rid of the "good" bacteria that fight infection. I was using antibacterial soap, so she advised me to buy Dove or some other non-scented, non-antibacterial soap.
She said to shower more than once a day. This is prolly not an option for a lot of mommies, but she said it helps.
As far as I can recall, that is all she advised. I hope it helps. If it is affecting your sex life, would it help to shower before bed, or before when you think you will have sex?