Or, put another way: should women be denied paid leave because they are medically unable to carry a child? That’s the nub of a lawsuit filed by a Long Island, N.Y., woman against her employer, a pharmaceutical company based in Lexington, Mass.

Kara Krill, a clinical business manager, is suing Cubist Pharmaceuticals for discrimination and breach of contract, among other complaints, claiming that the company denied her paid maternity leave to which she was entitled following the birth of her twins in May by a surrogate.

Krill had previously given birth to a child in 2007, but according to the suit she filed against Cubist in a U.S. District Court in Massachusetts, she was subsequently diagnosed with Asherman’s syndrome, a condition that often causes scar tissue in the uterus and results in reproductive disability. So when she and her husband decided to have another child, they turned to a surrogate.

Krill’s surrogate carried the biological offspring — twins, in this case — of Krill and her husband. Given that Krill received 13 weeks of paid maternity leave from Cubist after the birth of her first child, she said she expected a similar benefit after her twins arrived. Only this time she wasn’t delivering them, her surrogate was.

Cubist’s human resources department saw things differently. The company granted Krill five days of paid leave under the company’s adoption leave policy, but no paid time under the company’s maternity leave policy. According to court documents, Cubist offers parents five days of paid leave plus $4,000 for adoption costs under its adoption leave policy; the company gives new fathers the same amount of paid time for paternity leave.

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Krill’s complaint argues that since she and her husband are the biological parents of their children — the couple had obtained a prebirth order, signed by a judge, confirming the “legal and genetic parentage of Krill’s twins without having to institute adoption proceedings” — she should be given the same paid maternity leave benefits as every other biological mother in the company. Were it not for her disability, she would be receiving paid maternity leave, Krill argues.

Krill also says she was subjected to “verbal harassment and other adverse treatment” by her supervisor for pursuing maternity leave. Reported ABC News:

Her supervisor “told her pointedly on several different occasions that she should not be entitled to any leave from Cubist for the birth of her children, whether paid or unpaid,” according to court documents. When Krill informed her supervisor she was required to be with her newborn children for a minimum of 12 weeks, her supervisor told Krill that she could “‘put [her] twins in daycare,’ so she could come back to work sooner.'” Her supervisor also informed Krill she was “changing her sales quota expectations and taking away one of Krill’s largest customer accounts and assigning it to another Cubist employee who was not disabled, and not going out on maternity leave.”

Krill is seeking an injunction against getting fired and compensation and punitive damages for employment law violations.

Employers haven’t had to face many of these kinds of issues before, since surrogacy is still relatively uncommon in the U.S. — figures are fuzzy, but the Society for Assisted Reproductive Technology put the number of surrogate births at fewer than 300 a year in 2006.

Krill’s case will probably be decided on a fine reading of the company’s medical leave policies, but the imbroglio raises a larger question: what is the real reason for granting maternity leave?

If maternity leave is offered so that women can recover from what is, at best, the incredibly messy and strenuous business of giving birth, then new mothers like Krill who use surrogates would not really deserve paid leave, since they are not doing the hard yards of labor and delivery.

But paid maternity leave could also be regarded the same way as paid leave for jury duty — something a company does out of civic responsibility. Supporting new mothers as they bond with their children, learn to care for them and give them a good start is beneficial for society and for the survival of the species.

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Massachusetts does not mandate paid maternity leave, only unpaid. And in most workplaces, maternity leave is granted as part of a company’s provision for disability leave. But that’s always been a slightly odd arrangement, since bearing and delivering a child is one of the most able-bodied things a woman can do. (And having a child feels like having a disability only some of the time.)

Some mothers are outraged, viewing Cubist’s actions as discriminatory against women who are disabled and cannot medically bear their own children. But June Carbone, a law professor at the University of Missouri-Kansas City School of Law, told ABC News that she thinks the case is a tough one. “I can’t see that an employer would be able to provide women with maternity leave for the purpose of bonding with a child, where the woman has not given birth, and not be obligated to provide men with the same benefit,” she said.

Of course, there’s a solution for that: give new fathers more paid leave too.