These next five are case studies:
Cerebral atrophy in a vitamin B12-deficient infant of a vegetarian mother:
https://www.ncbi.nlm.nih.gov/pubmed/25076673Severe megaloblastic anemia in child breast fed by a vegetarian mother:
https://www.ncbi.nlm.nih.gov/pubmed/8442642Consequences of exclusive breast-feeding in vegan mother newborn - case report:
https://www.ncbi.nlm.nih.gov/pubmed/19748244Nutritional vitamin B12 deficiency in a breast-fed infant of a vegan-diet mother:
https://www.ncbi.nlm.nih.gov/pubmed/3948463"We report the case of a 7 month-old girl that presented with acute anemia, generalized muscular hypotonia and failure to thrive. Laboratory evaluation revealed cobalamin deficiency, due to a vegan diet of the mother."
https://www.ncbi.nlm.nih.gov/pubmed/18293883Most recent studies using more sensitive techniques for detecting B12 deficiency have found that 68% of vegetarians and 83% of vegans are B12 deficient, compared to just 5% of omnivores.
https://www.ncbi.nlm.nih.gov/pubmed/12816782https://www.ncbi.nlm.nih.gov/pubmed/10966896https://www.ncbi.nlm.nih.gov/pubmed/10552882On paper, calcium intake is similar in vegetarians and omnivores (probably because both eat dairy products), but is much lower in vegans, who are often deficient.
https://www.ncbi.nlm.nih.gov/pubmed/21139125http://ajcn.nutrition.org/content/70/3/543s.full