In AT&T Corp. v. Hulteen, the U.S. Supreme Court concluded that AT&T did not have to include an employee’s time on pregnancy leave prior to the enactment of the Pregnancy Discrimination Act when making pension calculations.  The Court’s opinion can be found here.  Scotus Blog has an opinion recap here.  Scotus Wiki has the case documents here.  The always reliable Connecticut Employment Law Blog has commentary on the limited relevance of the decision to employers today here.