Prenatal exposure to maternal hyperglycemia is associated with an increased risk of later adverse metabolic health. Changes in the regulation of peroxisome proliferator-activated receptor-γ coactivator-1α (PPARGC1A) in skeletal muscle and subcutaneous adipose tissue (SAT) is suggested to play a role in the developmental programming of dysmetabolism based on studies of human subjects exposed to an abnormal intrauterine environment (e.g., individuals with a low birth weight). We studied 206 adult offspring of women with gestational diabetes mellitus (O-GDM) or type 1 diabetes (O-T1D) and of women from the background population (O-BP) using a clinical examination, oral glucose tolerance test, and gene expression and DNA methylation of PPARGC1A in skeletal muscle and SAT. Plasma glucose was significantly higher for both O-GDM and O-T1D compared with O-BP (P < 0.05). PPARGC1A gene expression in muscle was lower in O-GDM compared with O-BP (P = 0.0003), whereas no differences were found between O-T1D and O-BP in either tissue. PPARGC1A DNA methylation percentages in muscle and SAT were similar among all groups. Decreased PPARGC1A gene expression in muscle has previously been associated with abnormal insulin function and may thus contribute to the increased risk of metabolic disease in O-GDM. The unaltered PPARGC1A gene expression in muscle of O-T1D suggests that factors other than intrauterine hyperglycemia may contribute to the decreased PPARGC1A expression in O-GDM.