Postpartum Metabolic Function in Women Delivering a Macrosomic Infant in the Absence of Gestational Diabetes Mellitus

OBJECTIVE: Gestational diabetes mellitus (GDM) is associated with fetal macrosomia and maternal postpartum dysglycemia, insulin resistance, and β-cell dysfunction. Indeed, in practice, a prior pregnancy that resulted in a large-for-gestational-age (LGA) delivery is often considered presumptive evidence of GDM, whether or not it was diagnosed at the time. If this clinical assumption is correct, however, we would expect these women to exhibit postpartum metabolic dysfunction. Thus, to test this hypothesis, we assessed metabolic function during and after pregnancy in a cohort of women stratified according to the presence/absence of GDM and LGA delivery, respectively. RESEARCH DESIGN AND METHODS: A total of 562 women underwent metabolic characterization, including oral glucose tolerance test (OGTT), in late pregnancy and at 3 months’ postpartum. The women were stratified into three groups: those with neither GDM nor LGA delivery (nonGDM, n = 364), those without GDM but with LGA delivery (nonGDM–LGA, n = 46), and those with GDM (n = 152). RESULTS: On logistic regression, GDM predicted postpartum glucose intolerance (OR 4.1 [95% CI 2.5–6.8]; P < 0.0001), whereas nonGDM–LGA did not (P = 0.65). At 3 months’ postpartum, the mean adjusted levels of fasting glucose and area under the glucose curve on the OGTT were significantly higher in the GDM women compared with either nonGDM or nonGDM–LGA (all P < 0.05), with no differences between the latter two groups. In a similar manner, mean adjusted insulin sensitivity (Matsuda index) and β-cell function (Insulin Secretion-Sensitivity Index-2) were lower in GDM women compared with either nonGDM or nonGDM–LGA (all P < 0.05), again with no differences between the latter two groups. CONCLUSIONS: Women with nonGDM–LGA do not exhibit postpartum metabolic dysfunction, arguing against the assumption of undiagnosed GDM in these patients.