Fetal Alcohol Syndrome Support Group
Fetal alcohol spectrum disorder (FASD) describes a spectrum of permanent and often devastating birth-defect syndromes caused when the pregnant mother consumes alcohol. The main effect of fetal alcohol exposure is brain damage, which can be caused during any trimester, because the fetus's brain continues to develop throughout the entire pregnancy.
So, FAS is not responsible for her sexual promiscuity, and it may be something related to your relationship.
Have you talked to her about this?
Have you two tried to get marriage counseling or regular counseling?
Have you tried spicing up your sex life?
Communication is the key if you want it to work.