Online health information systems (OHIS) have been proposed as a solution to reduce preventable maternal deaths by providing accessible and reliable health information. Data was collected through surveys administered annually from to . Statistical analysis included logistic regression models to assess mortality rates. During the study period, there was a significant reduction in preventable maternal deaths (p < 0.05) associated with improved access to OHIS information. The OHIS significantly contributed to reducing preventable maternal deaths by providing timely and accurate health information. Continued support for OHIS development is recommended to further enhance its effectiveness in maternal healthcare. Online Health Information Systems, Preventable Maternal Deaths, Nairobi, Kenya, Longitudinal Study Treatment effect was estimated with $\text{logit}(p_i)=\beta_0+\beta^\top X_i$, and uncertainty reported using confidence-interval based inference.