Thank you for your query at AskTheDoctor.com
I understand your concern.
For pregnancy to occur, vaginal intercourse with ejaculation inside the female vagina is mandatory.
Anal sex can't cause pregnancy as the semen can't meet the ovum.
So please do not worry.
Also, please use protection while having anal sex, as it increases the chances of both STDs and other infections, without protection.
Hope this was helpful,
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