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.

This is a multicenter, prospective cohort study including 204 pregnant women, with or without chronic kidney disease (CKD stages 2 to 4). Participants will be enrolled before 14 weeks of gestation. Blood samples (14 mL) will be collected at the 1st, 2nd, and 3rd trimesters and 2 months postpartum for kynurenine measurement, centrally analyzed at CHU Reims using LC-MS/MS. Additional data include maternal demographics, medical and obstetric history, anthropometry, laboratory data (creatinine, hemoglobin, hematocrit, proteinuria), blood pressure, ultrasound (growth parameters, umbilical artery Doppler), and maternal-fetal outcomes (preeclampsia, gestational hypertension, HELLP, hemorrhage, SGA, prematurity, mortality). The primary objective is to compare kynurenine concentrations in the 3rd trimester between women with and without CKD. Secondary objectives include describing longitudinal kynurenine evolution, its association with maternal-fetal outcomes, and modeling kynurenine needs during pregnancy in CKD.

Inclusion Criteria:

• Adult pregnant women <14 weeks of amenorrhea
• With or without CKD stage 2-4 (eGFR 15-89 mL/min/1.73m², diagnosed before pregnancy)
• Written informed consent
• Affiliation to a social security system

Exclusion Criteria:

• Multiple pregnancy
• Kidney transplantation
• Persons under guardianship or legal protection