From the Pittsburgh Urban Blog, via Chris Briem:
Between 2000 and 2010, only 20 of 130 municipalities in Allegheny County saw an increase in their populations under age 18. Ohio Township saw the largest percentage increase in its youth population, going from a population of 816 under age 18 to 1,190 in 2010. Glenfield Borough saw the largest percentage decline, going from a population under age 18 of 72 in 2000 to 38 in 2010.
Overall, the popualation under 18 for Allegheny County declined by just over 14% between 2000 and 2010. For the City of Pittsburgh, the population under age 18 declined by 25% over the same period.