Low fertility and delayed childbearing: Independent and combined effects on gestational diabetes risk in high-income women.

AIMS: Evidence on the independent and combined effects of low and delayed fertility on the risk of gestational diabetes mellitus (GDM) remains limited despite the increasing prevalence of these reproductive patterns in high-income populations. METHODS: We compared baseline and clinical characteristics of women with GDM and those with a normal oral glucose tolerance test who delivered at Abano Polyclinic, Italy, between January 2022 and August 2025. The independent and combined contributions of low parity and advanced maternal age to GDM risk were evaluated. RESULTS: Among 2,560 term women with low and delayed fertility, 231 (9.9%) developed GDM. Women with GDM were older than controls (36.0 [31.5-39.0] vs. 33.0 [30.0-37.0] years; P < 0.001), whereas parity was similar between groups. GDM prevalence increased progressively with maternal age, reaching 16.1% after 40 years. Kaplan-Meier analysis demonstrated a significant age-related increase in GDM probability (log-rank χ2 = 31.5, P < 0.001), with no age-parity interaction (P = 0.55). Women with GDM also had a higher BMI at delivery than controls (27.9 vs. 26.8 kg/m2), which remained independently associated with GDM after adjustment for maternal age and parity. CONCLUSIONS: Advanced maternal age and higher BMI at delivery are independent predictors of GDM in women with low and delayed fertility, supporting their inclusion in risk assessment and prevention strategies.