Vegetarian and vegan diets are becoming increasingly common among Danish women of reproductive age. We reviewed the available literature via PubMed and concluded that varied and well-balanced vegetarian and vegan diets are safe and sufficient during pregnancy and lactation, provided that dietary supplements for folate, vitamin B12, and vitamin D are taken regularly. Additionally, it is important to ensure adequate intake of calcium, protein, and iron. Protein requirements may be higher for vegetarians and especially for vegans, though evidence is limited regarding the recommendation for increased protein intake if the diet is exclusively plant-based. Routine blood tests are not recommended unless there has been insufficient supplementation leading up to or during pregnancy, or if symptoms suggest a deficiency. We found no evidence to support supplementation with docosahexaenoic acid (DHA). There is no indication of an increased risk of malformations for pregnant Danish women on a vegetarian or vegan diet compared to omnivores. The risk of delivering small for gestational age and low birthweight infants (<2500 grams) may be increased, but the evidence is conflicting and of poor quality. Vegetarian and vegan diets may offer benefits, such as a lower risk of excessive gestational weight gain and women consuming the lowest amounts of meat have a significantly lower risk of gestational diabetes. Vegans may face a lower risk of having large for gestational age infants. Vegetarian and vegan lifestyles are also compatible with breastfeeding, and provided women take the recommended supplements, there is no difference in the micronutrient content of the breast milk of vegetarian/vegan women compared to that of omnivores. Children of vegans and vegetarians with limited or no consumption of milk products or eggs are recommended to breastfeed or receive baby formula for at least the first two years of life.