Chronic kidney disease (CKD) affects more than 10% of the population worldwide and represents the second most important risk factor for preeclampsia, a life-threatening complication of pregnancy responsible for approximately 80,000 maternal and 500,000 perinatal deaths each year. Experimental studies have suggested a causal link between CKD, relative kynurenine deficiency during pregnancy, and preeclampsia development. Kynurenine, a tryptophan metabolite, plays a central role at the materno-fetal interface, supporting placental energy production, maternal-fetal immune tolerance, and placental perfusion. This study will prospectively assess and compare longitudinal kynurenine concentrations in pregnant women with and without CKD, and evaluate their associations with maternal and fetal outcomes.