In September 2006, Peggy Young sent her bosses at United Parcel Service a doctor's note advising her not to lift anything heavier than 20 pounds for the first 20 weeks of her pregnancy, and then no more than 10 pounds until she gave birth. Her job description, however, required her to heft packages heavier than that. Young was told she couldn't continue to work as a delivery driver while pregnant. UPS also rejected her request for a temporary reassignment to duties with less physical stress. So Young went on an unpaid leave of absence.

On Wednesday, in a case that could affect millions of working women who hope to have children, the Supreme Court heard Young's argument that UPS' refusal to accommodate her physical restrictions violated the Pregnancy Discrimination Act of 1978. The case turns on the nature of pregnancy. In 1976, the court ruled in General Electric Co. vs. Gilbert that pregnancy did not fall under the protections against gender bias included in Title VII of the Civil Rights Act of 1964. Two years later, Congress amended that law, making it clear that a pregnant woman must be accorded the same considerations as any "other persons not so affected but similar in their ability or inability to work."

UPS makes work accommodations for employees injured on the job, but not for those injured off the job. Its policy when Young worked there treated a pregnant woman the same way it treated a male driver who injured a knee in a weekend softball game — with an unpaid leave of absence until she could resume full duties. The lower courts ruled that policy acceptable, saying it reflected the law's ban on treating pregnant women differently.

But that's insufficient. Women should not be forced out of the workplace simply because they become pregnant. UPS, in fact, has come around to that position. It now offers light-duty accommodations to pregnant women who need them. At the very least, the Supreme Court should rule that pregnant women deserve to be treated as well as workers who are injured on the job. And if the court sides with UPS on this one, Congress should craft fresh legislation that — again — makes its intent clear.