Colloidal silver has been used successfully to resolve infertility (particularly infertility caused by internal infection). See this link: http://thesilveredge.com/cspreg.shtml
But I'm not so sure about using it while pregnant. Independent colloidal silver researcher Mark Metcalf used to publish a series of articles in which he routinely stated that colloidal silver was "good for the developing fetus." But try as I might, I could never find any research to back up that contention.