Pregnancy is possible whenever semen enters the vagina. If semen accidentally got into the vagina during anal sex, then yes, there would be a risk for pregnancy. Or, if some of the ejaculate leaked from the anus to the vaginal opening, there would be a risk of pregnancy.
If someone is using a form of birth control correctly, however, they are 99% protected from pregnancy. It would be a good idea to consider starting a form of birth control when engaging in sexual activity.
It is important to know that unprotected anal sex is a high risk activity for STI transmission. This is because the lining of the anus is very fragile and does not self lubricate. This makes it easier for what are called micro tears to occur during intercourse. These micro tears are small and someone may not feel them or know they are happening. Micro tears can create a direct line to someones blood, and can cause STI transmission.
It would be a good idea to use condoms during anal sex to reduce the risk of STI transmission. Using lubrication is also a good idea because lubrication helps reduce the risk of micro tears, and will help reduce the risk of the condom breaking. A person should use water based lubrication when using latex condoms. Oil based lubrication (like Vaseline, lotions, etc) will break down the material in the condom.
If you want to make an appointment at Teen Clinic give us a call at 303-442-5160