According to a study by the National Women's Law Center, a 25-year-old woman in the Lone Star State will pay as much as 22 percent more than men do when buying individual coverage if she is not covered under an employer's health plan. A 40-year-old woman will pay as much as 37 percent more.

"Women are being charged more, simply because they're women," said Judy Waxman, who worked on the study.

The study showed how gender rating in the insurance industry affects what women pay.

The insurance industry defends the practice, arguing that women, especially younger women, make more visits to the doctor, justifying the higher costs.

"At younger ages, women use more health care services and are prone to specific conditions," said Susan Paisano, of America's Health Insurance Plans, a group that represents the insurance industry.

Some doctors say they fear higher insurance costs will prevent women from buying coverage, leading them to skip routine care.

"If you have no insurance, you're going to deny the symptoms until the symptoms become so grave that you can no longer deny them and you end up going to the emergency room," said Dr. John Prosser, of Harris Methodist in Fort Worth.

Prosser said women with coverage are more likely to get check-ups and regular screenings for life-threatening conditions.

The cost differences go far beyond Texas. The authors of the study found 40-year-old-women pay as much as 48 percent more for individual insurance nationally. And in one state, Missouri, the study discovered women paid up 140 percent more than men.