Implanon (Single-Rod Implant)

Good review of Implanon, the single-rod implant. A few selected quotes:

Women in the United States have many safe and highly effective contraceptive choices. Nonetheless, approximately 50% of all pregnancies in the United States are unintended. Data from the 1995 National Survey of Family Growth indicate that the 3 million women who do not use any form of contraception account for 47% of these pregnancies, while 39 million contraception users account for 53%.

...

[Implanon] works primarily by inhibiting ovulation, although thickening of the cervical mucus also occurs. By contrast, multiple-rod implants [like Norplant] did not reliably inhibit ovulation, and relied primarily on cervical mucus thickening for their contraceptive effect.

...

Noncontraceptive benefits of the implant include improvements in dysmenorrhea [painful periods] and acne.

And for women who won't/can't use combination methods, yet are interested in [passive] menstrual management:

During the first 3 months of use, 30% to 40% of women become amenorrheic [no period] and remain so thereafter.

Overall, the following bleeding patterns were noted:

In the clinical trials, women experienced infrequent bleeding in 30% to 40% of the reference periods, making it the most common pattern experienced. The second most common pattern was amenorrhea, which occurred in about 20% of the reference periods. Prolonged and frequent bleeding occurred in 18% and 8% of the reference periods, respectively.