If the sidewalks seem less clogged with Bugaboo strollers these days and you can’t remember the last time you had to diaper a doll at a baby shower, it’s not your imagination or fuzzy memory. Birth rates in the U.S. fell 2% in 2008, the biggest drop in nearly four decades, and that trend is expected to continue. A new study out Sept. 23 from the Guttmacher Institute suggests that the timing is not a coincidence; the recession may be to blame, as women factor economic anxieties into their decision about having children.