Pennsylvania did not require all births to be recorded until 1906 when it was done by the State. Each county in Pennsylvania recorded births starting in 1893, but it was not strictly enforced and usually only births done by physicians were reported. Midwives, which were still very common at most births, sometimes reported births and sometimes didn't.
Before 1893 Pennsylvania briefly required births, marriages and deaths to be recorded from 1853 to ca 1855. Unfortunately it was decided it was too costly and the requirement was dropped. Otherwise, for the most part, the only places to find birth records in Pennsylvania before 1893 is in church records and family bibles.