WASHINGTON — Worried about birth control in light of headlines about side effects from Yaz and the patch? Women have a lot of options that are safe and effective, including some that are even more reliable.

You can choose a contraceptive that’s used daily, weekly, monthly, once every three months, once every three years, even once a decade.

Yet almost half of U.S. pregnancies are unintended — and experts say confusion and uncertainty despite all the options is a big reason.

“We have a whole generation now of young adults, the vast majority of whom are sexually active, who are in a fog about modern contraception,” says Sarah Brown of the National Campaign to Prevent Teen and Unplanned Pregnancy. “They don’t know enough to make a reasonable choice.”

Indeed, in a recent survey, the campaign found 42 percent of unmarried 18- to 29-year-olds said they knew little about birth control pills and two-thirds knew little about even more effective long-lasting contraceptives. A third said they believe there’s a good contraceptive for their personal needs but they don’t know which one.

Wonder how easy it is to use the NuvaRing, or what the once-every-three-months contraceptive shot costs? Can’t imagine how to insert the female condom? Want to know if the rhythm method has any chance of working? Or whether your partner could feel your IUD? What are the side effects, and which methods work best?

Those aren’t just questions for teens and young adults. Consider that half of girls are sexually active by age 17, and that menopause hits around 50. To avoid an unplanned pregnancy, the average American woman will have to use contraception for several decades. The right choice when you’re 20 might not still be when you’re 35 or 40.

And starting in 2013, affording different types may become easier as the new health care law requires insurance to cover contraception with no copays.

Today, sterilization, vasectomy for men and tube-tying for women, surprisingly is the nation’s leading form of birth control.

When it comes to reversible contraception, the pill is No. 1, highly effective if you take it correctly although missing doses raises the risk of pregnancy. The pill can bring other benefits as well. Long-term use lowers the risk of ovarian cancer; some types cut menstrual cramps or help clear acne.

But last week focused a lot of attention on birth control. First came the Obama administration’s decision to keep the Plan B morning-after pill — which can prevent pregnancy if taken soon enough after unprotected sex — behind pharmacy counters so only those 17 and older can get it without a prescription.

Then came two days of hearings about a rare but serious side effect of the pill and another hormone-containing contraceptive, the Ortho Evra patch. Advisers to the Food and Drug Administration recommended stronger warning labels on Yaz and similar new-generation birth control pills because they’re more likely than older, cheaper pills to cause dangerous blood clots. The FDA estimates that 10 in 10,000 women a year will get a clot on the newer drugs compared with 6 in 10,000 who take the older pills.

FDA’s advisers said the weekly patch may bring a somewhat higher clot risk, too, but called the patch an important option for women who have trouble sticking with a daily pill.

Brown points out that the contraceptives are less risky than getting pregnant.

When it comes to reliability, the most effective contraceptives may be two so-called long-acting products:

n The IUD, a little T-shaped device that sits in the uterus to block sperm.

n An implant called Implanon, a matchstick-sized hormone-emitting rod implanted in the arm.

You can forget about pregnancy for three years with Implanon and either five or 10 years with the IUD.

Change your mind about either type, and your doctor simply removes it.

But only a fraction of U.S. women use these long-acting contraceptives, 5.6 percent, according to the latest government data. In parts of Europe, they’re more popular.

Why not here? Partly, it’s the up-front cost. Partly, it’s a long-outdated belief that IUDs aren’t for young women. Or there may be a holdover effect from fears about the 1970s Dalkon shield, which was blamed for dangerous infections — although today’s brands are very safe.