Coffee is toxic stuff. De kun li primary study investigator said that he hopes the research will convince doctors to tell their pregnant patients to avoid coffee completely. Louis. Moreover the study found that even those women who consumed less than milligrams of caffeine daily had about percent increased risk for miscarriage. Expectant mothers have been confused for years about whether drinking that morning cup of joe could do harm to their unborn child. But does this study carry enough weight to finally answer the question of whether pregnant women should give up caffeine altogether dr.