Early Postpartum Glucose Tolerance Reclassification by Gestational Diabetes Subtype.

Importance: Gestational diabetes (GD) is a heterogeneous condition that predisposes both mother and offspring to metabolic disorders. GD subtypes defined by antepartum testing results have been associated with adverse perinatal outcomes, but little is known about their relationship to maternal metabolic outcomes soon after pregnancy. Objective: To evaluate early postpartum glucose tolerance reclassification of GD subtypes. Design, Setting, and Participants: This cohort study examined women from the Study of Women, Infant Feeding, and Type 2 Diabetes Mellitus After GD Pregnancy (SWIFT), who were recruited within the Kaiser Permanente Northern California integrated health care system between 2008 and 2011. All women were diagnosed with GD using Carpenter and Coustan criteria with complete glucose measurements at all 4 time points of the diagnostic 3-hour 100-gram oral glucose tolerance test (OGTT). Data analyses were conducted from January to July 2025. Exposure: Three subtypes of GD based on the diagnostic OGTT: (1) postload glucose intolerance (GD-P), as having elevations only at 2 or more postload time points; (2) fasting hyperglycemia (GD-F), as having elevations at fasting and 1 postload time point; and (3) both (GD-M), as having elevations at fasting and 2 or more post-load time points. Main Outcomes and Measures: At 6 to 9 weeks after delivery, glucose tolerance classification was evaluated using 2-hour, 75-g OGTTs. Modified Poisson regression models were used to estimate adjusted prevalence ratios (PRs) of postpartum prediabetes associated with GD subtypes, without and with adjustments for age, race and ethnicity, prepregnancy body mass index, educational level, and gestational weight gain. Results: This study included 1005 women with GD (median [IQR] age, 33.2 [29.8-36.7] years; 368 [36.6%] Asian, 78 [7.8%] Black, 308 [30.6%] Hispanic, 16 [1.6%] multiracial, and 235 [23.4%] White). Prevalence of postpartum prediabetes was 34.5% (347 women), with wide variation across GD subtypes; 23.9% (147 of 616), 41.9% (52 of 124), and 55.8% (148 of 265) for GD-P, GD-F, and GD-M, respectively. Compared with women with GD-P, the adjusted PR for GD-F was 1.74 (95% CI, 1.36-2.24), and for GD-M, it was 2.23 (95% CI, 1.85-2.68) (both P < .001). Pairwise comparisons between GD-F and GD-M were also statistically significant (adjusted PR, 1.28; 95% CI, 1.01-1.61; P = .04). Conclusions and Relevance: In this cohort study, GD subtypes had distinct postpartum prediabetes risks. Early action and intervention to address dysglycemia may be most beneficial for women with fasting or mixed defects.