The major concern would be the transmission of sexually transmitted diseases. Since there is commonly no barrier (i.e. a condom) for protection, any type of genital disease can be transmitted - gonorrhea, chlamydia, HIV, herpes, hepatitis, candidiasis (rarely), genital warts etc.
I would direct you to this article to further answer your question:
http://health.ivillage.com/sexualhealth/sxsafe/0,,6g90,00.html
Followup with your personal physician is essential.
This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.
Kevin, M.D.
http://www.straightfromthedoc.com