Beyond the demographic transition: regional convergence and structural shifts in adolescent fertility trends in Türkiye, 2009–2024

Adolescent fertility is a significant indicator of reproductive health, gender equity and social development. While Türkiye’s total fertility has declined below population replacement level, regional patterns of adolescent childbearing remain insufficiently understood. To examine adolescent fertility trends across Türkiye’s 13 NUTS-1 regions from 2009 to 2024, quantifying rates of decline, assessing regional convergence, and exploring the relationship with total fertility. Regional fertility indicators were reconstructed using official birth registration and population data. We calculated adolescent fertility rates (AFR, per 1000 women aged 15–19), adolescent birth share (percentage of total births), and total fertility rates (TFR). Temporal trends were estimated using log-linear regression. Regional convergence was assessed through dispersion analysis and fixed-effects panel regression. National AFR declined from 36.6 to 9.9 per 1000 (annual percentage change [APC] = − 8.4%; R2 = 0.99), while adolescent birth share fell from 8.8 to 3.3% (APC = − 6.6%; R2 = 0.98)—both far exceeding TFR decline from 2.08 to 1.48 children per woman (APC = − 2.3%; R2 = 0.83). The steepest reductions occurred in Northeast Anatolia (− 3.16 per year), Central East Anatolia (− 2.72), and Central Anatolia (− 2.63). Regional dispersion narrowed substantially: interquartile range for adolescent birth share contracted from 8–11% in 2009 to 4–6% in 2024. Adolescent birth share and TFR were strongly correlated (r = 0.71; Spearman ρ = 0.76), with fixed-effects regression confirming within-region associations (β = 0.561, p < 0.001; R2 = 0.97). However, adolescent fertility declined 2.3 times faster than total fertility, indicating that adolescent fertility declined even in regions where overall fertility changed minimally, suggesting that early-age childbearing trends do not mechanically mirror total fertility decline. Adolescent fertility in Türkiye declined at more than double the pace of overall fertility between 2009 and 2024, highlighting distinct temporal dynamics in early-age childbearing relative to overall fertility decline. However, persistent geographic disparities highlight the need for targeted, culturally sensitive reproductive health and educational interventions, particularly in southeastern provinces.