He was mocked so hard for suggesting this, that it gave its name to the Semmelweis effect: when a group rejects a measure or new knowledge because they don't see right away its efficiency or why it's true.
If I remember correctly, the reason he did suggest this is that he and his students used to work on corpses in between deliveries, and washed their hands to get rid of the smell. Then he noticed he had a lower death rate than his colleagues on babies and new mothers. Still, they put back in question his findings, some said he still had as many deaths, some acknowledged the difference in death ratio but claimed that this wasn't the reason, and mainly, washing hands was for pansies and suggesting people were dirty was insulting. He still kept doing it and eventually it was recognised that he'd been right all along.
If I remember correctly, the reason he did suggest this is that he and his students used to work on corpses in between deliveries, and washed their hands to get rid of the smell. Then he noticed he had a lower death rate than his colleagues on babies and new mothers. Still, they put back in question his findings, some said he still had as many deaths, some acknowledged the difference in death ratio but claimed that this wasn't the reason, and mainly, washing hands was for pansies and suggesting people were dirty was insulting. He still kept doing it and eventually it was recognised that he'd been right all along.
We really do live in a society.