Birth rate
According to the CIA's "The World Factbook", the country with the highest birth rate is Niger at 6.49 children born per woman and the country with the lowest birth rate is Taiwan, at 1.13 children born per woman.
Total fertility rate
The TFR of Singapore, Macau, Taiwan, Hong Kong and South Korea are the lowest in the world, with Singapore and Macau having a TFR below 1 in 2017. Japan too has a low TFR (1.45 in 2016). Singapore mitigates this through immigrant workers, but in Japan there is a serious demographic problem.