Data collected over 35 years shows that the use of intrauterine devices as emergency contraception has a 99.86 percent success rate. The findings prompted researchers at Princeton University to conclude that the devices could be routinely promoted as a defense against unwanted pregnancy.
More than a third of pregnancies worldwide and nearly half in the United States are unintended. —ARK
In a review of 35 years of data in which IUDs were inserted after unprotected intercourse, 99.86% of [women overall] did not become pregnant, reported Kelly Cleland, a research scientist at Princeton University in New Jersey, and colleagues in Human Reproduction.
Unintended pregnancy is a signicant problem, with at least 36% of pregnancies worldwide and nearly half of pregnancies in the U.S. being unintended, the authors noted in their introduction. Emergency contraception is a popular method for preventing unwanted pregnancy, with oral methods such as levonorgestrel (Plan B) and ulipristal acetate (Ella or EllaOne), among the leading medications used.
Although IUDs are another option, negative experiences with the Dalkon Shield in the 1970s led to years of low IUD use, the authors pointed out. But one of the major advantages of copper IUDs is that after placement for emergency contraception, the device can be left in and will continue to prevent pregnancy for at least a decade.