A senior sales representative for Merck & Co has sued the drugmaker for more than $100 million, alleging it discriminates against female employees in terms of pay and advancement, particularly pregnant employees and women with children.

The lawsuit, filed on Thursday in U.S. District Court for the District of New Jersey, alleges the No. 2 U.S. drugmaker engages in "systematic, companywide discriminatory treatment of its female employees on the basis of their gender and their taking federal and state-protected pregnancy leave."

Merck officials could not be reached immediately for comment.

Plaintiff Kelli Smith is described in the lawsuit as a senior sales rep in Merck's Toms River, New Jersey, district, who has been a top performer in terms of sales.

Smith alleged she was demoted for taking maternity leave in 2010, and penalized by unfair performance evaluations and other actions that stalled her career and hurt her reputation.

The suit alleged Merck's companywide sales incentive plan "provides that the compensation of managers and directors is decreased when their employees take legally protected leave ... Through this centralized policy, Merck discourages management from hiring and promoting women."

Smith is represented by the law firm of Sanford Heisler, which won a May 2010 lawsuit that made similar claims against Swiss drugmaker Novartis AG .

Novartis was ordered to pay $250 million in punitive damages after a federal jury in Manhattan found the company had discriminated against thousands of female sales reps in terms of pay, promotions and pregnancy policies.

(Reporting by Ransdell Pierson; editing by John Wallace)