Modified relaxin polypeptides and uses thereof are provided. In particular, modified relaxin polypeptide variants having substitutions with a non-naturally encoded amino acid in the A or B chain, especially residues 1, 5, 13, 18 and B chain residue 7. The non-natural amino acid is preferably a phenylalanine analog, especially para-acetyl-phenylalanine (pAcF or pAF). The relaxin variants are linked to compounds to improve their pharmacological properties, especially PEG having an average MW of between about 5 kDa and about 40 kDa , which is linked to the non-naturally encoded amino acid.
