Birth rate
As of 2017, Niger has the highest birth rate in the world with 49.443 per thousand people. 
Japan has one of the lowest birth rates in the world with 8 per thousand people.
While in Japan there are 126 million people and in Niger 21 million, both countries had around 1 million babies born in 2016.
Prevalence of teenage pregnancy
The UK has one of the highest teenage birth rates in Europe with a rate of 26.4 teenage births per 1,000 women aged 15–19 in 2006, down from 27.9 births in 2001. The UK also has a higher rate of abortion than most European countries. Of young Britons reported engaging in sexual intercourse whilst in their teens, 80% said they did not use a form of contraception (Citation needed), although a half of those under 16, and one-third of those between 16 and 19, said they did not use a form of contraception during their first encounter (Citation needed). 10% of British teen mothers are married. Adolescent pregnancy is viewed as a matter of concern by both the British government and the British press.