LANSING, Mich. — Michigan’s state Board of Canvassers certified a controversial petition Monday that would require women to buy an additional rider on their health insurance if they want abortion coverage.

The issue moves to the Michigan Legislature, which could act this week to enact the law without the approval or signature of Gov. Rick Snyder, who has opposed the measure.

Since the Legislature has strong anti-abortion majorities in both the state House and Senate, it has a good chance of passing and immediately becoming law. A majority of the members in both chambers signed the petition.

If the proposal becomes law, it would require all private and public health-insurance plans to offer a separate rider for abortion. People would then have to buy that rider before knowing whether they would ever need an abortion and wouldn’t be able to buy the rider after getting pregnant by any means, including rape or incest.

The Guttmacher Institute, a New York-based agency that tracks public policy regarding women’s health and reproductive rights, reported that eight other states have instituted policies that prohibit public and private insurance plans from including abortion coverage in health-care policies. Another 15 prohibit the coverage in insurance purchased through the health exchanges set up through the Affordable Care Act.

The Michigan secretary of state reported that Michigan Right to Life, which spearheaded the petition drive, has more than enough valid signatures to start the ball rolling on the new state law. A minimum of 258,088 valid signatures were needed. The anti-abortion activists turned in 315,477 signatures, and the secretary of state’s elections division estimated that 299,941 of the signatures are valid.

The state Board of Canvassers unanimously voted to certify the results. The Legislature is expected to receive the petition when it returns from a two-week break Tuesday.

The Legislature added the optional abortion-rider language into a bill last year that transformed Blue Cross Blue Shield (BCBS) into a nonprofit mutual insurer. And even though the BCBS bill was a priority for Snyder, he vetoed the bill because of the abortion language.

If the Legislature rejects or takes no action on the legislative ballot initiative, it will go to the November 2014 ballot for a statewide vote.