Today, the Supreme Court ruled that family-owned businesses cannot be required to provide their employees with health insurance plans that offer contraception coverage if that's against their owners' religious beliefs. The decision may have the effect of actually leading to more abortions, experts say.

The owners of arts-and-crafts chain Hobby Lobby, the business at the center of the controversial case at the Supreme Court, said they believe that two forms of birth control — emergency contraceptives, which can be taken after sex, and intrauterine devices (IUDs) — can cause abortions because they may work by preventing a fertilized egg from implanting in the uterus.

But in the case of emergency contraception, robust scientific evidence maintains the drugs do not work by preventing implantation, but instead by stopping ovulation. This suggests people who believe emergency contraceptives (available under the brand names Plan B and ella) cause abortions mostly have misconceptions about the drugs' mechanism of action, doctors say. [7 Surprising Facts about the Pill]

"They are simply wrong. Scientifically, they are wrong," said Dr. Ellen Wiebe, a clinician and professor of reproductive health at the University of British Columbia in Vancouver, Canada. "The emergency contraception, Plan B and ella, only stop ovulation. These medications do not interfere with implantation."

The science of birth control

Plan B and ella work only 60 to 70 percent of the time, because people may have had sex after the ovulation has already occurred.

IUDs are more effective in preventing pregnancy, and usually work by keeping sperm away from the egg, but can also prevent a fertilized egg from implanting in the uterus, if the device is inserted after fertilization.

This makes the mechanism of action of IUD as emergency contraception tantamount to abortion in some religious views, such as those held by the owners of Hobby Lobby. However, this view of abortion stands in contrast with the one held by the U.S. government and by medical professionals' organizations, which don't consider a woman pregnant before the fertilized egg has implanted in the uterus.

Experts said that today's decision may result in more abortions than if the family-owned businesses were required to offer insurance plans that cover these contraceptives. That's because studies show a major reason that women forgo using contraceptives is because of cost issues. The IUDs can cost up to $1,000, and the monthly cost of birth control pills can be difficult for families with low incomes.

A rise in unintended pregnancies?

If the financial barrier to contraception is not lifted by another entity, such as the government, some women who can't afford birth control may see consequences.

"Certainly, the rate of unintended pregnancies would go up, and a logical conclusion would be that abortion rates would go up, too," said Dr. Susan Rubin, an assistant professor of family and social medicine at Albert Einstein College of Medicine and an attending physician in family medicine at Montefiore Medical Center in New York City.

Wiebe said the court's ruling almost guarantees that there will be more abortions among employees who don't get coverage for contraception.

"We have really good evidence for that. If you use science here, you're talking about this decision increasing the number of women having abortion if they do not cover emergency contraception and IUDs."

The evidence comes from studies that examined whether rates of abortions fell if women received the most effective methods of contraception, free of charge. In one research project, conducted in the St. Louis area in Missouri, of the 10,000 participating women, 75 percent opted for long-acting methods of contraception such as IUDs or implants, and the rest chose short-acting methods such as pills, hormonal patches or cervical rings.

The results showed that increasing the availability and use of the most effective contraception methods, such as IUDs, reduced abortion rates by 20 percent, Wiebe said.

In the court's decision, justices suggested that one alternative to employers offering women contraception coverage could be for the government to assume the costs.

"It's really leaving these women with nothing, at least for now," Rubin said.

Email Bahar Gholipour. Follow Live Science @livescience, Facebook& Google+. Originally published on Live Science.