Does taking prenatal vitamins before you conceive reduce the risk of miscarriage?

No: It does not reduce risk of miscarriage, but it does reduce risk of certain birth defects related to vitamin deficiency. The most common among these is spina bifida caused by a folic acid (folate) deficiency. This prevents the spinal cord from fully forming. It's a common birth defect in developing countries but is essentially eliminated with simple prenatal vitamins.