The present invention relates to ultrathin fluid-absorbent cores comprising a substrate layer, water-absorbent polymer particles and an adhesive, wherein the water-absorbent polymer particles comprise a basic salt of a polyvalent metal cation and a monovalent carboxylic acid anion on the surface and the wet SAP shake out of water-absorbent polymer particles out of the fluid-absorbent core is less than 10% by weight.