Johnson Controls, Inc. (Johnson) (defendant), a battery manufacturer, maintained a policy first discouraging and later outright prohibiting women employees from taking jobs that involved exposure to the mineral lead, a main ingredient in batteries. This policy was based on known health risks related to occupational lead exposure, which included harm to unborn fetuses. In its fetal-protection policy, Johnson defined women as all women capable of becoming pregnant; it excluded only women who could provide medical documentation of their inability to bear children. A number of Johnson employees (plaintiffs) challenged the policy. The plaintiffs included a woman who had been sterilized in order to avoid losing her job, a woman who had experienced a pay cut when she was transferred out of a lead-exposed job, and a man who was denied a leave of absence that he had sought in order to lower his lead levels before becoming a father. The district court granted summary judgment in favor of Johnson. The United States Court of Appeals for the Seventh Circuit affirmed, holding that Johnson’s fetal-protection policy was justifiable as a business necessity. The plaintiffs petitioned for review by the United States Supreme Court.