I'd put my money on contraception and a change in family dynamics being the biggest contributors, here. See, back in those times, people had lots of kids to support their families and businesses. They'd get kids popping out as soon as possible, so they could get older and get jobs and help raise the even younger kids. This was especially important on farms and with family businesses because the more workers they had who were in the family, the fewer workers they have to pay. All they have to do is feed them. And if they own a business, all the money they would be taking away if they were an outsider working would stay within the family and thus the business. That is why you'll see so many families back then had 5, 9, even 12 and 15 kids. It was all about getting as many workers as you could.The Lesbian Flower said:-snip-
There are plenty of couples and families having babies, still. But due to a decrease in the need for them, and the need for so many, there are now fewer being born. Even if the same number of married couples have children, it would make all the difference in the world if now they're having 1 or 2 instead of 5 or 10.