There is no current consensus on the optimal dietary selenium supplement for use in clinical supplementation because bioavailability and effects on expression of the various selenoproteins depend on the form of selenium product used. A small UK-based RCT of selenium supplementation (selenium in pregnancy; Systolic Blood Pressure Intervention Trial) is ongoing. Although not powered to demonstrate clinical benefit, this study is designed to assess the impact of selenium supplements on preeclampsia related biomarkers. If successful, a larger multicenter RCT adequately powered to detect differences in the rates of preeclampsia will be needed to assess the potential clinical benefit