Social conflict caused by early fertility in Russia

The relevance of the work is due to the fact that a few centuries ago, early pregnancy was not considered something shameful and wrong. People lived in economic and social conditions where an extra pair of hands was always necessary. Life expectancy was shorter than it is now, so people had to think about offspring from an early age. Moreover, even now, in the rapidly developing modern world, there are many countries (most of them belong to the "third world" countries) where early fertility is still considered the norm. Some young girls don't even have time to finish school when they become mothers. But what other reasons can make the young modern people to become parents until the legal age of majority?