<prompt> As per etiological classification of diabetes mellitus, Gestational diabetes mellitus isType IAType IBType IIType IV  <response>: Etiologic Classification of Diabetes MellitusI. Type 1 diabetes beta cell destruction, usually leading to absolute insulin deficiencyImmune-mediatedIdiopathicII. Type 2 diabetes may range from predominantly insulin resistance with relative insulin deficiency to a predominantly insulin secretory defect with insulin resistanceIII. Other specific types of diabetesGenetic defects of beta cell development or function characterized by mutations in:Genetic defects in insulin actionDiseases of the exocrine pancreas--pancreatitis, pancreatectomy, neoplasia, cystic fibrosis, hemochromatosis, fibrocalculous pancreatopathy, mutations in carboxyl ester lipaseEndocrinopathies--acromegaly, Cushings syndrome, glucagonoma, pheochromocytoma, hypehyroidism, somatostatinoma, aldosteronomaDrug- or chemical-induced- Glucocoicoids, vacor a rodenticide, pentamidine, nicotinic acid, diazoxide, b-adrenergic agonists, thiazides, calcineurin and mTOR inhibitors, hydantoins, asparaginase, a-interferon, protease inhibitors, antipsychotics atypicals and others, epinephrineInfections--ongenital rubella, cytomegalovirus, coxsackievirusUncommon forms of immune-mediated diabetes--stiff-person syndrome, anti-insulin receptor antibodiesOther genetic syndromes sometimes associated with diabetes--IV. Gestational diabetes mellitus GDMRef: Harrison 19e pg: 2399 