Does woman release oxytocin whenever they have intercourse?

Yes, and even before. Oxytocin is also released into the blood during many types of touching; including cuddling, hugging, kissing, orgasm, sex and snuggling. The physical effects of oxytocin include increased sensitivity of nerve endings, stimulated muscle contractions, increased heart rate plus the desire to touch and be touched. It is often called the "bonding" hormone. Men also release it during orgasm.