BBC will be airing a show Tuesday 10/18 about this...

Spain is reeling from an avalanche of allegations of baby theft and baby trafficking. The trade began at the end of the Spanish civil war and continued for 50 years - hundreds of thousands of babies are thought to have been traded by nuns, priests and doctors up to the 1990s.
BBC - BBC Two Programmes - This World, Spain's Stolen Babies



An online search for "300,000 babies stolen by the Catholic church in Spain" will have more detail than the above article