Looking for Japan's missing third baby boom.

Aim: High-income countries are now experiencing a decline in fertility. After experiencing baby booms in 1947-1949 and 1971-1974, Japan's population has been decreasing since 2015. In an attempt to predict the next baby boom, we searched for any upward demographic trends occurring after 1974.

Methods: We analyzed time trends of the numbers and rates of live births, stillbirths and induced abortions using Japanese government data from 1975 to 2014. We then selected two birth cohorts: the first baby boomers who were 0-4 years old in 1950, and the second baby boomers who were 0-4 years old in 1975, and analyzed their rates of live births, stillbirths, and abortions by five-year age groups.

Results: There was no upswing in the numbers of births, stillbirths, or induced abortions; however, the abortion rate increased during 1996-2002. Compared with the first baby boomer cohort, the second baby boomer cohort had half the peak live birth rate for the same age group (25-29 years old), and half the peak rate of abortions, with a shift toward a younger age group (20-24).

Conclusions: This analysis of Japanese fertility trends derived from all pregnancy outcomes showed no upward trend in fertility in Japan since 1974.