Lisa Neidert and colleagues discuss the factors affecting birth rates and population change in the U.S. When asked whether the recent dip in fertility to below replacement level represents “cause for alarm,” Neidert says growth in the rate of childlessness and population aging make fertility trends a new story in the U.S. ([Audio: Neidert’s comments begin at 4:40 mark](http://audio2.ideastream.org/wcpn/2013/0828soi.mp3).)