I thought everyone is aware of that. Life of a Slavic man is sadly, similar to a life of an American black man [1], for the same reasons - poverty, low educational level, lack of opportunities, which causes crime and self-destructing behavior. Which results in that by the age of marriage, there is a shortage of men at least as bad as a shortage of black men in U.S. - except black women have a slim chance of getting into an interracial marriage - getting a European or other foreign guy for a Russian girl is more difficult.
Coupled with sexism meaning that women typically earn very little if anything, and their only chance to escape abject poverty is to get married, and because there are so many women for so few men and with nothing else to make the guy interested, pregnancy becomes the only option. To keep the guy married (especially given that divorce laws are very weak and not in general working in post-Soviet countries, and men lose little if they divorce), an extreme psychological pressure is required, which usually takes efforts of the whole girl's family. Except the very cynical guys, only chance to escape this is to keep as far from marriage as possible. This is probably why post-soviet population declines so fast.
Of course, the higher classes of society (e.g. coders) are exempt.
(the other side of this is domestic violence which is very common, and sometimes not even viewed as a problem, which is an even more sad side of the story)