Several studies in pregnant women and early childhood suggest that vitamin D deficiency (serum 25-hydroxyvitamin D levels <50 nmol/l) is common in both population groups. Recent recommendations have therefore reviewed the literature regarding the role of vitamin D in pregnant women and in early childhood. The Institute of Medicine, in their most recent assessment in 2010, recommended 600 IU per day in pregnant and lactating women. In 2011, the US Endocrine Task Force on Vitamin D commented that 600 IU per day may not be sufficient to correct vitamin D deficiency in pregnant and lactating women. Their recommendation was 1,500-2,000 IU vitamin D per day in pregnant and lactating women with vitamin D deficiency. For infants, the recommendation from both societies is consistently 400 IU vitamin D per day, and also in children both societies recommend 600 IU vitamin D per day. This review will summarize the scientific basis that led to the most recent recommendations.