One is that medical societies, like the American College of Obstetricians and Gynecologists (ACOG), have endorsed IUDs and implants.

ACOG says the devices should be offered as "first-line" options for most women, because of their effectiveness and safety.

Another reason, Finer said, is that advertisements have probably increased women's awareness of IUDs.

IUDs are implanted in the uterus, where they release small amounts of either copper or the hormone progestin to prevent pregnancy. The contraceptive implant, about the size of a matchstick, is inserted under the skin of the arm, where it releases controlled amounts of progestin.

The hormonal IUD, sold under the brand name Mirena, can prevent pregnancy for five years, while the copper version, sold as ParaGard, is effective for about 10 years. The contraceptive implant, sold as Implanon, works for three years.

Finer said the devices are "substantially" more effective than the Pill or condoms because they do not rely on perfect use.