It's a very well-documented fact that, when a society becomes affluent and urbanized, its birth rate drops. This has been going on for hundreds of years--long before artificial contraception was popular (which leads me to believe that people were engaging in other, non-technological means of contraception). Children are an economic asset to a traditional farm family, because they work on the farm. They are an economic burden to an urban family, because they cost money and don't produce anything. If we are to prevent our society from contracepting itself out of existence, we are going to have to develop social policies to keep large families out of poverty.
This isn't entirely true, because if you look at the 17th -18th century in France, and in particular in Paris and the other cities there was an illegitimacy boom. The majority of adults never married (yes, I was surprised too when I learned this) as the economic and social circumstances made raising a family very difficult. For this reason there was a rise in prostitution and illicit sex, and thus an explosion of bastard babies. This became such a problem that you had the rise of the great orphanages, complete with anonymous drop-off 'turns.'
The idea that most people used to be married, in the way it is commonly thought of in the 1950's was only a modern phenomenon. Most people at this time and perhaps even before this in Europe were single. They obviously didn't contracept but had the babies and just abandoned them.
On another note, this article neglects to mention the aggressive recruitment of international students going on all over the world to fill in the missing seats of domestic students at North American public schools and universities. This is a common strategy to help schools balance their budget at the end of the year.