Can taking large amounts of vitamin c induce a miscarriage at 6 weeks?

Possibly: Research is limited but many women report that high doses of vitamin C (500 mg an hour) for several days taken in early pregnancy induces miscarriage. Thus, if one wants to avoid miscarriage then avoid high doses of C in early pregnancy. If one wishes to induce miscarriage it is safe to try but probably works less than 50% of the time. See http://www.sisterzeus.com/vit_c_ab.html for more info.