To shed light on the determinants of teenage pregnancy, I analyze the dynamic fertility effects of Argentina's National Plan for the Prevention of Unintentional Pregnancy in Adolescence (ENIA). ENIA consisted of in-service secondary teacher training in comprehensive sex education, in-school walk-in advisements with private and confidential referrals to the health system, an expansion of long-acting reversible contraceptives (LARC) and in-service adolescent-appropriate health practitioners training. Exploiting differences in official birth records to females aged 15 to 19 across counties induced by the arbitrary timing and target of the program, I estimate significant reductions in births of 10% on average starting after 9 months from adoption —the expected length of a pregnancy. I analyze school censuses leveraging between-school, across-county and time variation, and the cointegration between treatment effects and aggregate insertion of LARC. Findings suggest that both school-based interventions and LARC expansion were necessary to explain the results, likely by relaxing adolescent-specific constraints to fertility control. I show that ENIA was effective in pro-life counties and provinces with an absolute legislative majority voting against abortion legalization. In contrast, I estimate null effects or even increases in birth rates in less-conservative treated counties in the Buenos Aires Metropolitan Area where teenage pregnancy may respond to different constraints or birth intentions.