title: Study: no link between folic acid and twins.
mesh_terms: D005260:Female; D005492:Folic Acid / Q000008:administration & dosage*; D006801:Humans; D016742:Preconception Care; D016135:Spinal Dysraphism / Q000517:prevention & control; D014427:Twins
chemical_list: D005492:Folic Acid