Transmission is usually Sexual: Direct transmission through sexual intercourse Needle - or instrument-related: Sharing of blood-contaminated needles or exposure to contaminated instruments Transfusion - or transplant-related Vertical: Transmission from an infected mother to child during pregnancy, childbirth, or through breast milk Sexual transmission of HIV Sexual practices such as fellatio (oral sex done to a male) and cunnilingus (oral sex done to a female) appear to be relatively low risk but not absolutely safe (see table).