What is calculated by dividing the number of late fetal deaths after 28 weeks and infant deaths within 7 days of birth by the number of live births plus late fetal deaths during a year?

The perinatal mortality rate is calculated by dividing the number of late fetal deaths after 28 weeks of gestation and infant deaths within the first 7 days after birth by the total number of live births combined with late fetal deaths during the same year. This calculation provides valuable insight into the health outcomes surrounding the perinatal period, which includes the time shortly before and after birth.

The reason this is the correct answer lies in the definitions: perinatal mortality encompasses both late fetal deaths and early infant deaths. By using the live births and late fetal deaths in the denominator, the rate reflects the risk of both these tragic outcomes in relation to those who are born or stillbirths that could have been born alive.

In contrast, other terms such as fetal mortality rate focus solely on fetal deaths, while infant fertility rate does not pertain directly to mortality but rather to live births in relation to the reproductive population. Maternal mortality rate specifically refers to the deaths of mothers due to complications of pregnancy and childbirth. Each of these other concepts measures different outcomes and populations, which distinguishes the perinatal mortality rate as the correct and most relevant measure in this context.