I am not absolutely sure whether or not there are any definite benefits or any detriments to taking colloidal silver during pregnancy. The fact that it has been theorized that colloidal silver helps regenerate tissue via converting cells back to stem cells might be reason for caution. One must remember that everything a mother breathes, eats or drinks as well as any toxins encountered in household items and so forth will make their way to the fetus.
I personally believe that, other than good all around whole food and whole food derived nutrition, an expectant mother should use extreme caution in any supplements they take.
Given your stated preference for crude large particle homemade silver with a nine volt battery, I would suggest extra caution. We certainly would not want to see a "blue baby".
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.