Background: Inadequate reproductive health understanding among teenager. It is indicated through the escalation number of free sex behavior which leads to the increasing of teenage pregnancy and childbirth whether around the urban or suburb area. As well as the increasing number of teenage marriage. Objective: To find out the relationship between reproductive health understanding and teenage childbirth rate. Method: Descriptive correlational method using cross sectional approach. Women in labor of under 18 years old across Balikpapan city were taken as samples. There were 56 research subjects collected with purposive sampling technique. Research variables include the independent variable: reproductive health understanding and dependent variable: teenage childbirth. Chi square was applied to verify the data with significance limit: P < 0,05. Result: Teenage childbirth rate with inadequate understanding were 77,6% and 22,4% with adequate understanding. Among adult childbirth, there were 81,0% acquired adequate understanding and only 19,0% with inadequate understanding about reproductive health. There was a significant relation between reproductive health understanding and the age of labor. Conclusion: The correlation and significant relationship are detected between reproductive health understanding toward the teenage childbirth rate.