KPmetabolites were mainly investigated in maternal blood, in the second and thirdtrimester of pregnancy, while data on first-trimester KP metabolites were scarce.Compared to uncomplicated pregnancies, a low maternal tryptophan concentration wasassociated with depression, GDM, FGR, PTB, and SA, while a high tryptophanconcentration was associated with PIH. This evidence concerns the gene NPPA and major depressive disorder.