Process for manufacturing a polymer by polycondensation of a hydroxy acid, said polymer comprising at least 80% by weight of units that correspond to the hydroxy acid, according to which at least one polyfunctional reactant capable of giving rise to the formation of a three-dimensional polymer network is mixed with the hydroxy acid, and according to which the mixture is subjected to temperature and pressure conditions and for a duration which are all suitable for giving rise to the formation of the network. Poly(hydroxy acid) (PHA) obtainable by such a process.