Iodine sufficiency is particularly important in pregnancy, where median urinary iodine concentration (UIC) in the range of 150–250 µg/L indicates adequate iodine status. The aims of this study were to determine UIC and assess if dietary and maternal characteristics influence the iodine status in pregnant Norwegian women. The study comprises a cross-sectional population-based prospective cohort of pregnant women (Little in Norway (LiN)). Median UIC in 954 urine samples was 85 µg/L and 78.4% of the samples (n = 748) were ≤150 µg/L. 23.2% (n = 221) of the samples were ≤50 µg/L and 5.2% (n = 50) were above the requirements of iodine intake (>250 µg/L). Frequent iodine-supplement users (n = 144) had significantly higher UIC (120 µg/L) than non-frequent users (75 µg/L). Frequent milk and dairy product consumers (4–9 portions/day) had significantly higher UIC (99 µg/L) than women consuming 0–1 portion/day (57 µg/L) or 2–3 portions/day (83 µg/L). Women living in mid-Norway (n = 255) had lowest UIC (72 µg/L). In conclusion, this study shows that the diet of the pregnant women did not necessarily secure a sufficient iodine intake. There is an urgent need for public health strategies to secure adequate iodine nutrition among pregnant women in Norway.