SACRAMENTO  (AP) — California women who take birth control would have to make fewer trips to the pharmacy under a bill that would require insurers to cover up to a 12-month supply at one time.

Supporters say for birth control to be most effective, it must be taken consistently and argue the longer-term supply would reduce the potential for skipped doses and would lower instances of unintended pregnancy.

“Women are smart enough to carefully administer and use these drugs appropriately,” said Democratic Sen. Fran Pavley of Agoura Hills, the bill’s author.

She said limiting birth control to 30- or 90-day supplies — the current industry standard — may have made sense in the 1970s, when “the pill” came on the market and was unproven, but she’s surprised it’s still in practice.

“They’ve been measured and reformed and are safe,” Pavley said.

There’s no health-related reason why the supplies should be limited to shorter periods, and eliminating repeat trips to the pharmacy is more convenient, she added.

Unlike many other medications, experts say one missed dose of a contraceptive can undo months of careful usage.

At least five states and Washington, D.C., have approved legislation allowing such extended supplies.

Two lobbying groups representing insurers, the Association of California Life and Health Insurance Companies and the California Association of Health Plans, oppose the measure, SB999, in its current form.

The groups have asked the author to change the bill to allow insurers to request a patient be stabilized on the drug before filling the full year’s dosage. They also want to delay the start date of the measure by a year to Jan. 1, 2018.

Between 10 and 33 percent of women try more than one birth control method within a 12-month period, according to member companies, said Steffanie Watkins, vice president of health policy for the Association of California Life and Health Insurance Companies.

“We want to ensure women are on the medicine that they should be on and want to make sure it’s done in a thoughtful way,” she said.

Supporters argue the bill does not require women to get a year’s worth of contraception and instead calls for supplies of “up to” 12 months. Of the states that have passed similar legislation, only Oregon and Maryland include provisions for a smaller initial amount before filling the longer supply.

The California Right to Life Committee sees no need for a year’s supply, said director Camille Giglio. In a letter to the state Senate Health Committee, the organization wrote contraceptives can have “devastating consequences” on women’s health.

Giglio also said she was concerned that expanded access to contraception could lead to an increase in sex trafficking.

In 2013, the Centers for Disease Control and Prevention recommended prescribing or providing up to a year’s supply of pill packs at each visit. The report suggested that common insurance restrictions could result in unwanted discontinuation of birth control and increased risk of pregnancy.

California’s legislation has cleared the state Senate and needs to pass the Assembly before the end of August to go before Gov. Jerry Brown for his consideration. It would include Medi-Cal managed plans and cover hormonal contraceptives including the pill, vaginal ring and contraceptive patch.

A 2011 University of California, San Francisco, study of women in a state family planning program found that a one-year supply of contraceptives led to a 30 percent reduction in unintended pregnancies and a 46 percent decrease in the abortion rate, as compared to 30- or 90-day supplies.

“We need to do all we can to ensure that every child is a wanted child, and part of that is being able to use birth control as effectively as possible,” said Amy Everitt, state director of NARAL Pro-Choice California.