5.3.2.0 One-‍Step Strat­e­gy

The IADPSG defined di­ag­nos­tic cut points for GDM as the av­er­age fast­ing, 1-h, and 2-h PG val­ues dur­ing a 75-g OGTT in women at 24–28 weeks of ges­ta­tion who par­tic­i­pat­ed in the HAPO study at which odds for ad­verse out­comes reached 1.75 times the es­ti­mat­ed odds of these out­comes at the mean fast­ing, 1-h, and 2-h PG lev­els of the study pop­u­la­tion. This one-‍step strat­e­gy was an­tic­i­pat­ed to significant­ly in­crease the in­ci­dence of GDM (from 5–6% to 15–20%), pri­mar­i­ly be­cause only one abnor­mal value, not two, be­came sufficient to make the di­ag­no­sis (75). The an­tic­i­pat­ed in­crease in the in­ci­dence of GDM could have a sub­stan­tial im­pact on costs and med­i­cal in­fras­truc­ture needs and has the po­ten­tial to “med­i­calize” preg­nan­cies pre­vi­ous­ly cat­e­go­rized as nor­mal. A re­cent fol­low-‍up study of women par­tic­i­pat­ing in a blind­ed study of preg­nan­cy OGTTs found that 11 years after their preg­nan­cies, women who would have been di­ag­nosed with GDM by the one-‍step ap­proach, as com­pared with those with­out, were at 3.4-fold high­er risk of de­vel­op­ing predi­a­betes and type 2 di­a­betes and had chil­dren with a high­er risk of obe­si­ty and in­creased body fat, sug­gest­ing that the larg­er group of women iden­tified by the one-‍step ap­proach would benefit from in­creased screen­ing for di­a­betes and predi­a­betes that would ac­com­pa­ny a his­to­ry of GDM (76). Nev­er­the­less, the ADA rec­om­mends these di­ag­nos­tic cri­te­ria with the in­tent of op­ti­miz­ing ges­ta­tional out­comes be­cause these cri­te­ria were the only ones based on preg­nan­cy out­comes rather than end points such as pre­diction of sub­se­quent ma­ter­nal di­a­betes.

The ex­pect­ed benefits to the off­spring are in­ferred from in­ter­ven­tion tri­als that fo­cused on women with lower lev­els of hy­per­glycemia than iden­tified using older GDM di­ag­nos­tic cri­te­ria. Those tri­als found mod­est benefits in­clud­ing re­duced rates of large-for-ges­ta­tional-age births and preeclamp­sia (77,78). It is im­por­tant to note that 80–90% of women being treat­ed for mild GDM in these two ran­domized con­trolled tri­als could be man­aged with lifestyle ther­a­py alone. The OGTT glu­cose cut­offs in these two tri­als over­lapped with the thresh­olds rec­om­mend­ed by the IADPSG, and in one trial (78), the 2-h PG thresh­old (140 mg/dL [7.8 mmol/‍L]) was lower than the cut­off rec­om­mend­ed by the IADPSG (153 mg/dL [8.5 mmol/‍L]). No ran­domized con­trolled tri­als of iden­tifying and treat­ing GDM using the IADPSG cri­te­ria ver­sus older cri­te­ria have been pub­lished to date. Data are also lack­ing on how the treat­ment of lower lev­els of hy­per­glycemia af­fects a moth­er’s fu­ture risk for the de­vel­op­ment of type 2 di­a­betes and her off­spring’s risk for obe­si­ty, di­a­betes, and other metabol­ic dis­or­ders. Ad­di­tion­al well-‍de­signed clin­i­cal stud­ies are need­ed to de­ter­mine the op­ti­mal in­ten­si­ty of mon­i­tor­ing and treat­ment of women with GDM di­ag­nosed by the one-‍step strat­e­gy (79,80).