5.2.0.0 Defini­tion

For many years, GDM was defined as any de­gree of glu­cose intol­er­ance that was first rec­og­nized dur­ing preg­nan­cy (40), re­gard­less of whether the con­di­tion may have pre­dat­ed the preg­nan­cy or per­sist­ed after the preg­nan­cy. This defini­tion fa­cil­i­tat­ed a uni­form strat­e­gy for de­tec­tion and clas­sification of GDM, but it was lim­it­ed by im­pre­ci­sion.

The on­go­ing epi­dem­ic of obe­si­ty and di­a­betes has led to more type 2 di­a­betes in women of child­bear­ing age, with an in­crease in the num­ber of preg­nant women with undi­ag­nosed type 2 di­a­betes (66). Be­cause of the num­ber of preg­nant women with undi­ag­nosed type 2 di­a­betes, it is rea­son­able to test women with risk fac­tors for type 2 di­a­betes (67) (Table 2.3) at their ini­tial pre­na­tal visit, using stan­dard di­ag­nos­tic cri­te­ria (Table 2.2). Women di­ag­nosed with di­a­betes by stan­dard di­ag­nos­tic cri­te­ria in the first trimester should be clas­sified as hav­ing pre­ex­ist­ing preges­ta­tional di­a­betes (type 2 di­a­betes or, very rarely, type 1 di­a­betes or mono­genic di­a­betes). Women found to have predi­a­betes in the first trimester may be en­cour­aged to make lifestyle changes to re­duce their risk of de­vel­op­ing type 2 di­a­betes, and per­haps GDM, though more study is need­ed (68). GDM is di­a­betes that is first di­ag­nosed in the sec­ond or third trimester of preg­nan­cy that is not clear­ly ei­ther pre­ex­ist­ing type 1 or type 2 di­a­betes (see Sec­tion 14 “Man­age­ment of Di­a­betes in Preg­nan­cy”). The In­ter­na­tion­al As­so­ci­a­tion of the Di­a­betes and Preg­nan­cy Study Groups (IADPSG) GDM di­ag­nos­tic cri­te­ria for the 75-g OGTT as well as the GDM screen­ing and di­ag­nos­tic cri­te­ria used in the two-‍step ap­proach were not de­rived from data in the first half of preg­nan­cy, so the di­ag­no­sis of GDM in early preg­nan­cy by ei­ther FPG or OGTT val­ues is not ev­i­dence based (69).

Be­cause GDM con­fers in­creased risk for the de­vel­op­ment of type 2 di­a­betes after de­liv­ery (70,71) and be­cause ef­fec­tive pre­ven­tion in­ter­ven­tions are avail­able (72,73), women di­ag­nosed with GDM should re­ceive life­long screen­ing for predi­a­betes and type 2 di­a­betes.