US women's labor force participation rate is now under that of Japan, which we think of as being unfriendly to working women. The cost of childcare is a big factor in America, which given the world-historically low birthrates in Japan are presumably less of an issue there.

https://www.washingtonpost.com/news/wonk/wp/2015/10/07/how-american-women-fell-behind-japanese-women-in-the-workplace/

Women participation in the labor force going down AND birth rates going down are two alarming demographic trends in the United States that I had no idea were happening until now. 

So then what's the reason for US women leaving the workplace if birthrates are also decreasing here?  Doesn't make sense for childrearing to be the reason if it's declining too.