Read this before you rely on a doctor's interpretation of your blood tests or your child's. This book highlights that a mother deficient in b12, due to diet or genetics, can cause her child to be deficient in b12. Combine this with a food supply fortified with folic acid (an inferior form of folate many people cannot metabolise) and you are risking a masked b12 deficiency. This book, combined with a blood test and a dietary review for mother and child, plus 23andme genetic testing, could give the answers to countless families around the world and possibly explain why their children are needlessly suffering from developmental delay. I thank the authors for this book, you are making a difference one by one, I only wish all children with developmental delay and their mothers would be tested and better still, women who are pregnant or thinking of getting pregnant.