From Dionne Scott at the Center for Reproductive Rights:
Four women who entered the workforce prior to the enactment of the Pregnancy Discrimination Act (PDA) are disputing AT & T’s calculation of their pensions. That calculation was based on a pre-PDA policy which denied the women full credit during their maternity leaves.
The Center for Reproductive Rights wrote a brief that informs the Court of substantive equality principles, arguing that prior to 1976 (before PDA was enacted), it was the uniform view of the federal courts of appeals and the EEOC that discrimination based on pregnancy constituted sex discrimination within the meaning of Title VII (which protects individuals against employment discrimination on the bases of race and color, as well as national origin, sex, and religion).
PDA, enacted in 1978, only confirmed that this view of Title VII was correct.