Objective: To compare dietary magnesium intake and magnesium concentrations in serum, red blood cells (RBC) and urine during pregnancy of women habitually following a long-term plant-based diet and of women following an average Western (control) diet. Design: Prospective study during pregnancy. Setting: Giessen, Germany. Subjects: Healthy pregnant women (n ¼ 108) in their 9-12th, 20-22nd and 36-38th gestational week habitually following a plant-based diet for more than 3 y or an average Western diet. The vegetarians were subdivided into ovo-lacto vegetarians (n ¼ 27) and low-meat eaters (n ¼ 43). Results: Significant higher dietary magnesium intakes were observed in pregnant women consuming a plant-based diet (508714 mg/day for ovo-lacto vegetarians, Po0.001 and 504711 mg/day for low-meat eaters, Po0.001) than in pregnant women consuming a control diet (41279 mg/day). Serum magnesium concentrations were similar in all diet groups whereas RBC magnesium was slightly higher in low-meat eaters than in controls (P ¼ 0.058). Urinary magnesium excretion was higher in ovo-lacto vegetarians (P ¼ 0.023), followed by low-meat eaters (P ¼ 0.017) when compared to the control group. During the third trimester of pregnancy, the frequency and the occurrence of calf cramps was lower in the plant-based diet group than in the control group (P ¼ 0.004 and 0.008). Conclusions: Owing to a higher dietary magnesium intake confirmed by higher urinary magnesium excretion, habitual plantbased diets result in a slightly improved magnesium status during pregnancy and reduce the frequency of calf cramps during the third trimester of pregnancy compared to an average Western diet. Therefore, plant-based diets during pregnancy can be recommended with regard to magnesium supply.