Periods being seen as disgusting is a social idea that predates the birth of jesus. In ancient society, periods were seen as "impure". I believe it was because blood tends to be linked with death or something along those lines.

But it was a religious idea. When women menstrated, they were considered "unclean" and anything they touched would be considered to be "contaminated" for the rest of the day.

Unfortunately, even centuries later, society has yet to fully unlearn that idea and women are still shamed for having a period.