"There are some links between vegetarians and lower birthweight and earlier labour"
ncbi.nlm.nih.gov/pubmed/7788369
Effects of vitamin B12 and folate deficiency on brain development in children:
ncbi.nlm.nih.gov/pmc/articles/PMC3137939/
"Particular attention should be paid to adequate protein intake and sources of essential fatty acids, iron, zinc, calcium, and vitamins B12 and D. Supplementation may be required in cases of strict vegetarian diets with no intake of any animal products."
ncbi.nlm.nih.gov/pmc/articles/PMC2912628/
These next five are case studies:
Cerebral atrophy in a vitamin B12-deficient infant of a vegetarian mother:
ncbi.nlm.nih.gov/pubmed/25076673
Severe megaloblastic anemia in child breast fed by a vegetarian mother:
ncbi.nlm.nih.gov/pubmed/8442642
Consequences of exclusive breast-feeding in vegan mother newborn - case report:
ncbi.nlm.nih.gov/pubmed/19748244
Nutritional vitamin B12 deficiency in a breast-fed infant of a vegan-diet mother:
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."
ncbi.nlm.nih.gov/pubmed/18293883
Most 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. ncbi.nlm.nih.gov/pubmed/12816782
ncbi.nlm.nih.gov/pubmed/10966896
ncbi.nlm.nih.gov/pubmed/10552882
On 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.
ncbi.nlm.nih.gov/pubmed/21139125
ajcn.nutrition.org/content/70/3/543s.full