Using contractors also can cut benefits costs: they typically aren't eligible for such benefits as health insurance and paid maternity leave.

WSJ: Payroll Audits Put Employers on Edge

Within four years, for example, none of the state's major carriers offered individual insurance plans that included maternity coverage.

WSJ: Peter Suderman: The Lesson of State Health-Care Reforms

Health reform also requires plans in the individual insurance market to cover maternity care, which only about 13 percent of such plans did in 2009.

FORBES: Health Ruling Hailed Except on Medicaid Rules

The new insurance exchanges created by this law ensure coverage of preventive care and basic health services, including maternity care, which is often not provided in health plans in the individual insurance market.

WHITEHOUSE: The White House

The mandate would apply to health plans sold through the state's insurance exchange, and elsewhere, that include maternity coverage.

WSJ: States Harden Views Over Laws Governing Abortion

Insurance plans in the new exchange must cover maternity benefits.

WHITEHOUSE: Eliminating Obstacles to the Care Women Need

Many workers, like Ms. Stoll, believe that as independent business owners they might not be able to afford insurance that covers all their medical needs, such as maternity or mental-health care.

WSJ: Will Health-Care Law Beget Entrepreneurs?

"If their employer is not paying employers' National Insurance, unbeknownst to them they may not then be entitled to statutory maternity pay if they become pregnant, they may not be entitled to statutory sick pay if they fall ill, " he said.

BBC: Tax loophole for UK businesses set to close

The Affordable Care Act states that all insurance sold on state exchanges must cover ten basic things, such as emergency care, maternity care, and so on.

FORBES: Here's How Stripping Down Health Care Reform Benefits to the Bare Bones Will Backfire and Drive Up Costs