Question

why is maternal mortality not a rate but a ratio?differentiate between incidence risk and incidence rate

Answer 1

• The WHO defines maternal mortality as the death of women while pregnant or within 42 days of termination of pregnancy irrespective of duration and time of pregnancy. A ratio is a value obtained by dividing one quantity with others. The maternal mortality rate is not possible to measure because the total number of pregnancies are not predictable. So the ratio is considered as a proxy. Maternal mortality ratio is measured by dividing the number of maternal death regardless of its outcome by the number of live birth in a population.

• Incidence risk is the measure of disease occurrence over a defined period of time. While the incidence rate shows the time an individual is at risk.

Incidence risk is the total number of new cases in a defined time period divided by the population at risk at the beginning of defined time period.

Incidence risk = number of new cases in specific period of time ÷ number of persons at risk at the beginning of that time period.

Incidence rate measures the number of new cases in a population by the sum of time each participant remained under observation and risk of developing the outcome during the observation.

Incidence rate = number of new cases in given time period ÷ total person- time at risk during observation period.