Ancaps and Abortion

For those ancaps who view abortion as murder and a violation of the NAP, how—if at all—do you imagine abortion might be detected without an intrusive and non-voluntery surveillance system?

ie, how might someone go about identifying pregnancies that the pregnant person does not publicly disclose? How do you determine if someone purposefully or accidentally ate lunchmeat contaminated with listeria that can trigger an abortion?

If abortion is murder, then it is unique among murder in that it can that can involve only one publicly observable person and can be difficult to distinguish diagnostically from purely natural outcomes or innocuous choices.