2.2. Diagnostic and exclusion criteria

AMA was defined as maternal age ≥35 years at delivery. Non‐AMA was defined as maternal age <35 years at delivery. GDM was defined as an oral glucose tolerance test of 75 g at 24–28 weeks of gestation according to the International Association of Diabetes and Pregnancy Study Group. Any one of the following criteria was used to diagnose GDM: fasting ≥92 mg/dL (5.10 mmol/L), 1 h ≥180 mg/dL (10.00 mmol/L), or 2 h ≥153 mg/dL (8.50 mmol/L). ¹⁹

Patients with a history of tumor resection, congenital dysfunction, mental disorder, liver damage, hepatitis, syphilis, and other infectious diseases before pregnancy were excluded. Women with twin or multiple pregnancies or who underwent in vitro fertilization (IVF) were excluded because of the intrinsic risk of multiple pregnancies and IVF. Patients with incomplete information were also excluded (Figure 1).

Flow chart of the selection of 34,602 pregnant women in this study. AGDM, advanced maternal age with gestational diabetes mellitus; non‐AGDM, advanced maternal age without gestational diabetes mellitus; non‐YGDM, young pregnant women without gestational diabetes mellitus; YGDM, young pregnant women with gestational diabetes mellitus.