Dr. Omedi Gilbert2026-03-242026-03-2420242581-9615https://ir.gretsauniversity.ac.ke/handle/123456789/289ResearchStudy purpose: To establish the contribution of high-risk fertility behavior on infant mortality in Kenya. Methodology: The study used cross-sectional survey data obtained from the 2022 Kenya demographic and health survey. Descriptive analysis involved frequencies and cross-tabulation. Inferential analysis involved multinomial logistic regression. Results: Young age at first birth of under-20 years was significantly related to neonatal (OR = 1.001; ; CI = 0.347-0.850), post-neonatal (OR = 1.542; ; CI = 0.364-0.809), and infant (OR = 1.043; ; CI = 0.372-0.791) mortalities. Mothers who gave birth under-20 years of age had higher odds of experiencing neonatal mortality (OR = 1.183; ; CI = 0.374-1.733). Births of orders 2 to 3 had lower odds of neonatal (OR = 0.710; ; CI = 0.436-1.157) and infant (OR = 0.802; ; CI = 0.494-1.304) mortalities. Nulliparous women were 0.31 times less likely and 0.45 times more likely, to report neonatal and post-neonatal mortalities, respectively. Conclusion: Analytical findings revealed under- birth, underorder births, and births to nulliparous women to be high-risk fertility behaviors related to infant mortality. Old age at first birth and preceding birth interval were unrelated to infant mortality. Advocacy on the need to delay entry into marriage and sexual debut should be done so as to address the issues of child brides and young age at first birth. Keywords: Age at first birth; Age at motherhood; Birth order; Parity; Preceding birth interval; Infant mortality