Hastie CE, Mackay DF, Clemens TL, et al. - Studies have described a variation in the risk of preeclampsia by month of delivery. Researchers herein examined if maternal vitamin D concentration mediates this seasonal patterning by using antenatal exposure to UV‐B radiation as an instrumental variable. They linked Scottish maternity records to antenatal UV‐B exposure derived from satellites between 2000 and 2010. They identified 522,896 eligible singleton deliveries to be included in this study; preeclampsia developed in 8,689 (1.66%) mothers. Total antenatal UV‐B exposure ranging from 43.18 to 101.11 kJ/m² was recorded and its association with decreased risk of preeclampsia was observed with evidence of a dose‐response relationship. They identified associations for UV‐B exposure in all 3 trimesters. Findings overall support the possibility that the seasonal patterning of preeclampsia may be mediated through low maternal vitamin D concentration in winter resulting from low UV‐B radiation.