Why Don't More Minnesota Teens Use IUDs?Over the past three or four years, the medical community has reached a consensus about the best method for teenage girls to avoid unplanned pregnancies. Long-acting birth control devices -- IUDs and under-the-skin implants -- function for years without requiring any effort by women. Their effectivity rate, more than 99 percent, is surpassed only by sterility and celibacy. Teens who’ve used the devices prefer them to other contraceptives. And while the price of a single device is upward of $800, their long-term cost is among the lowest of any birth control method.