In contrast to prevalence, it quantifies the number of new events or cases of disease that develop in a population of individuals at risk during a specified time interval (typically a year and cases per 100,000), including those who die later or migrate out. Rates are calculated using life births or total births as the denominator. To re-emphasize: incidence should not be confused with prevalence. Incidence contains information about the risk of contracting a disease while prevalence indicates how widespread it is. Generally speaking, incidence is more useful than prevalence in understanding the etiology of a disease [e.g., if the incidence of a disease in a population increases, then it can be assumed that there is a risk factor (or constellation of risk factors) responsible for this change].
See Birth prevalence, Cumulative incidence (CI), Epidemiology, Hypoxic-ischemic encephalopathy, Incidence, Neuronal migration disorders, Placenta previa, Prevalence, Risk factors