why do we not conclude that husband #1 had syphilis, given the biochem bent, and get on with life, carefully

I think what Milan wanted to do was write a female romance heroine who had no interest in "babies ever after," which is fine! But the whole reason she was anti-babies is because she was basically made that way via excessive trauma, which sort of negates the whole "I don't want kids and that's totally normal and okay" moral. (Also . . . Sebastian, you don't actually have to use the pull-out method. Condoms! They work!)