Vitamin D is important for bone health, as well as an increasing number of other health outcomes. Here we discuss the evidence relating to vitamin D in pregnancy, from preconception to the perinatal period. During pregnancy extra calcium required for fetal skeletal growth is attained by both maternal bone resorption and increased absorption from dietary sources, necessitating increased maternal vitamin D. Many women have low vitamin D status during pregnancy and may require supplementation, although optimal serum levels and intake required to achieve those levels is not yet well defined. Evidence from animal studies, with some supportive human evidence, suggests that fertility may be impaired in mothers with low vitamin D. During pregnancy, maintaining vitamin D and calcium levels may decrease the risks of pre-eclampsia, while gestational diabetes mellitus appears to be more common in those with low vitamin D status, although there is insufficient evidence of causality. The evidence in relation to increased risks of bacterial vaginosis and caesarean section similarly requires confirmation in carefully designed observational and experimental studies. This review outlines the emerging evidence that maternal vitamin D status during pregnancy is important for the health of the mother and offspring across a range of possible health outcomes.