While it's purely speculation on my part, I would suggest that you are probably worrying needlessly. I say this as I find it unlikely that the prostitute would want to get pregnant solely to collect child support.
However, if she were to be pregnant, then yes, she could pursue you for child support. This, of course, presumes that she knows who you are and/or can find you to bring you into court. If so, she could request a DNA test, establish paternity and then obtain a court order requiring you to pay support.
This can be a rather complex issue, please let me know if anything requires clarification.
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