This can be written in active form. Alternate translation: "if she has defined herself by committing" (See: [[rc://en/ta/man/translate/figs-activepassive]])
Here the "sin" refers specifically to committing adultery. The meaning of this statement can be made clear. Alternate translation: "committed adultery" (See: [[rc://en/ta/man/translate/figs-explicit]])
Possible meanings are 1) that the woman will become unable to have children or 2) that the woman's pregnancy will end too early and the baby will die. Here the word "thigh" is a polite way of referring to the woman's womb or her private parts. (See: [[rc://en/ta/man/translate/figs-euphemism]]) See how you translated these concepts in [Numbers 5:21](./21.md).