Myla Nauman has the same job, the same boss, and the same customers as when she worked for Abbott Laboratories. But since Abbott spun off her division as a separate firm last spring, the 22-year veteran of the company and other workers have agonized over long-anticipated retirement benefits that got left behind.

The scenario faced by Ms. Nauman and her co-workers – now filling the ranks of a freestanding hospital products company Abbott dubbed Hospira Inc. – is becoming increasingly common as more companies curtail pension and retiree health benefits. Hospira told workers soon after the spin-off it was freezing their accrual of pension benefits and eliminating retiree health care for many of them, even as Abbott maintained the benefits for remaining employees.

But the situation at Abbott and Hospira – subjects of a lawsuit by Ms. Nauman, a Southern California saleswoman, and two co-workers – illustrates how much has changed in recent years in the way companies treat their pension obligations. And it raises troubling questions as American businesses embark on a new round of mergers, acquisitions, and restructuring: Could such changes offer employers an added opportunity, or perhaps even be a justification in themselves, to unload burdensome retirement benefits?

“Every year it was reinforced to me that I was working with a promise and at my retirement … that I would have full retirement benefits and all the pension benefits I’d earned,” said Ms. Nauman, who lives in Valley Center, Calif. “I was almost at the finish line when all the promises were broken.”

Whether escaping retirement obligations motivated Abbott’s spin-off goes to a key part of the company’s identity. The pharmaceutical and health care product maker has long promoted itself as a very generous employer. Its corporate Web site notes proudly that it was named No. 3 on Money magazine’s lists of companies with the best employee benefits.

But that honor was awarded back in 2002, and much has changed at the company and in the economic environment its executives must navigate.

Scores of companies have moved, in recent years, to shed themselves of employee benefits obligations. They’ve been motivated partly by skyrocketing health care costs and by interest rates and meager stock market returns that have undermined their ability to keep pace with soaring future pension obligations.

“These special benefits are what have encouraged employees to stay with companies for their entire careers,” said Karen Ferguson, director of the Pension Rights Center, an advocacy group. “What is not par for the course is not making good on your promises. That is what’s changed, and doing it because, in the short-term, it looks good on the company’s books.”

As workers at numerous companies have learned to their dismay, the federal law on employee benefits gives employers the right to make changes in their retirement plans at any time, provided those changes affect all workers without discrimination. But even in situations like the one at Abbott where benefits are reduced or eliminated, workers retain the right to pension benefits they have already earned.

Companies buy and sell businesses all the time, a fact also recognized by the law. In such cases, workers shifted in such an arrangement are deemed terminated by their original employer, allowing the new company to set the terms of their benefits.

But in their lawsuit, filed in November in the U.S. District Court for the Northern District of Illinois, Ms. Nauman and her co-workers accuse Abbott and Hospira of plotting the spin-off specifically to discriminate against them. The move, they say, was designed as cover for depriving Abbott’s oldest workers of their rightful benefits.

They point to several events, including a conference call on September 22, 2003 – a month after the spin-off was announced – during which Abbott executives fielded questions from worried workers. During that call, the workers say, a top personnel executive confirmed that the hospital products division slated for spin-off was the “most senior division” in the company, noting that about 70% of its 14,000 workers were 40 or older.

That was obvious to workers long before the spin-off. Michael Loughery of Carmel, Ind., a Hospira sales representative who has also joined in the suit, said that at joint meetings with salespeople from other divisions, hospital products staffers stood out as the ones with the gray hair, and comprised most of those whose retirements were announced to the group.

The suit also draws attention to the first time Hospira reported its earnings to holders of its freshly minted shares, in August of last year. Roughly a third of the company’s profits for that quarter was due to a “one-time, non-cash curtailment gain” of $40.4 million, resulting from its elimination of retiree health care benefits.

Abbott and Hospira adamantly defend the spin-off as a sound business decision that complied with benefits law.

“Abbott created Hospira as an independent company to provide shareholders with equity investments in two separate companies that are focused exclusively on maximizing opportunities in their distinct markets,” Abbott said in a written statement. “Allegations that Hospira was created for any other purpose are unfounded and without merit.”

The benefit cuts put Hospira employees on par with workers at competing firms and are part of efforts to “help manage costs and support Hospira’s long-term growth,” Stacey Eisen, a spokeswoman for the new company, said in an e-mail response to questions.

Ms. Eisen and a spokesman for Abbott both declined to comment on specific allegations in the lawsuits. The companies both say they will fight the suit, and recently filed motions to have it dismissed.

The workers who sued say the spin-off was at least as much about cutting benefit costs as for strategic business reasons.

“Once you start putting a pencil to that, to what those employees personally have accrued and will continue to accrue, you start to see the huge financial gain that Abbott is going to gain by spinning off this division. I absolutely believe that’s the reason it was done,” said Jane Roller, a Houston sales representative who joined the suit.

Only Hospira workers at least 50 with 10 years of service retained future retiree health benefits in the shift. But only their years of service at Abbott will be used to determine how much they will pay for those benefits. That means workers like Mr. Loughery, who is 53, now expect to pay nearly half of health insurance premiums on retirement, compared to the 12% Abbott retirees are paying, he said.

He estimates that he will be eligible for a monthly pension check of about $1,700 once he turns 65 – compared with the roughly $3,800 a month he expected to pocket by staying with Abbott until turning 65 and accruing further benefits.

Abbott’s spin-off of Hospira is not the first time a company has been accused of reorganizing its business for the purpose of unloading benefit costs.

In probably the most notorious case, managers at Continental Can Co. in the late 1970s and early 1980s used a sophisticated computer program they called BELL – reverse code for Let’s Limit Employee Benefits – to target for closure plants employing workers just about to reach retirement age or whose pension benefits were ready to vest.

Workers sued, and the company finally settled in 1991 for $415 million.

In a closely watched case settled in 2003, McDonnell Douglas Corp. agreed to pay $36 million to settle charges that it closed a Tulsa, Okla., factory as a way to detach itself from an older workforce on the verge of claiming expensive retirement benefits.

Recently, older workers at a joint venture of Halliburton Corp. and Ingersoll-Rand have lodged complaints about the way their pension benefits were handled. When Halliburton sold its interest in the business, Dresser-Rand, to its partner in 2000, it was able to free itself from early retirement benefits many of the workers were on the verge of acquiring.

But employment lawyers and pension experts say the Abbott-Hospira case has few direct parallels, a sign that companies long handled spin-offs or sales of division very differently.