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.
Rivne Oblast
Rivne is one of the regions with the highest birth rate in all of Ukraine. The heavy rural (about two thirds of the population is rural) and ethnic Ukrainian (close to 95%) composition of the population might be responsible for this. However the birth rate is not uniform across Rivne, with raions like Ostroh having extremely low birth rates (9.7 per 1000) and other raions like Rokytnivskyi having extremely high birth rates (24.0 per 1000).