Improving early prenatal and postnatal conditions account for at least 16% to 17% of the decline in ten-year mortality rates of 60–79-year-olds between 1900 and 1960–1980. Historical trends in early prenatal and postnatal conditions imply that while the baby-boom cohort may be particularly long-lived compared to past cohorts, mortality rates may not fall as steeply for the cohorts born after 1955 as for earlier cohorts. (JEL: J15, N31)