Veganism causes loss of libido and erectile dysfunction:

https://www.ncbi.nlm.nih.gov/pubmed/21353476
Children who are raised on strict vegan diets do not grow normally:

https://www.ncbi.nlm.nih.gov/pubmed/4067152
https://www.ncbi.nlm.nih.gov/pubmed/8005079

Children develop rickets after prolonged periods of strict vegetarian diets:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1874810/pdf/canmedaj01383-0052.pdf

"There are some links between vegetarians and lower birthweight and earlier labour"

https://www.ncbi.nlm.nih.gov/pubmed/7788369

Effects of vitamin B12 and folate deficiency on brain development in children:

https://www.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."