It does seem that that's a bit of doctrine that isn't enforced these days. [link|http://www.leaflets.on.ca/marriage.htm|This] page lists 8 necessary conditions for a valid Catholic marriage. #7 is:
7. Who intend to have a family
There are certainly people out there who would like to have children and are unable to. I don't think that the Catholic church demands annulments of marriages in those cases, but wouldn't be surprised if it was different in earlier times.
Thanks.
Cheers,
Scott.