Teenage pregnancies in Kenyan urban slums are a significant public health concern with high rates of unintended and unsafe pregnancies. Comprehensive sexual healthcare services are essential for teenage mothers to address reproductive, mental, and social needs effectively. A mixed-methods approach was employed including surveys, focus group discussions, and interviews with stakeholders. Data were analysed using thematic content analysis for qualitative data and descriptive statistics for quantitative data. The implementation of comprehensive sexual healthcare services led to a significant increase in contraceptive use among teenage mothers from 20% pre-intervention to 65% post-intervention (95% CI: 48-79%). Comprehensive sexual healthcare services significantly improved the reproductive health outcomes for teenage mothers, with notable increases in contraceptive uptake. Scaling up these comprehensive sexual healthcare services is recommended to address ongoing challenges and enhance community well-being. Teenage pregnancy, urban slums, comprehensive sexual healthcare, contraception, mental health support Treatment effect was estimated with $\text{logit}(p_i)=\beta_0+\beta^\top X_i$, and uncertainty reported using confidence-interval based inference.