A lesbian employee of St. Joseph’s Medical Center in Westchester County filed a class-action lawsuit on Tuesday claiming that her spouse is entitled to the same medical coverage as the spouses of heterosexual employees.

Since same-sex marriage became legal in New York last July, most companies in the state have extended spousal health benefits to same-sex couples. But self-insured employers, which include St. Joseph’s and other large institutions, are primarily governed by federal, not state regulations. As a result, they may deny health coverage to same-sex couples under the federal Defense of Marriage Act, which defines marriage as a union between a man and a woman. In the lawsuit, filed in Federal District Court in Manhattan, the employee argued that it was illegal to use the Defense of Marriage Act to justify denial of coverage, because the law is discriminatory and therefore unconstitutional.

“I’m not just thinking about our particular situation,” said the hospital employee, who has filed the lawsuit using a pseudonym, Jane Roe, and spoke on condition of anonymity because she said she was concerned about the impact on her job if she complained publicly. The woman has been with her partner for 16 years, she said, and married her last autumn.

“I’m also thinking about the folks who are behind us, the younger people in their 20s and 30s, who are thinking about getting married and who are going to have the same problem,” she said. “It’s just not socially fair.”