HARRISBURG — Pennsylvania lost a single congressional seat as a result of census figures released today, the smallest reduction in its delegation in seven decades.

Reapportionment figures cut the state’s number of congressmen from 19 to 18 for the 2012 election, despite slight growth over the past decade in Pennsylvania’s total population, from 12.3 million to 12.7 million. The state’s growth rate of 3.4 percent lagged far behind the national rate of 12.7 percent.

The loss of only one seat is the fewest Pennsylvania has shed since 1940, when the number also fell by one, to 33. There were 36 Pennsylvania congressmen in the 1910s and 1920s.

In every other census since 1950, Pennsylvania has lost either two or three of its representatives in Washington.

The state Legislature and governor will have to decide over the coming year how to redraw the lines of the state’s congressional districts, a process that will require precinct-level population figures that are not expected to be released for several months.

The changes are handled as legislation, and are subject to the governor’s veto.