Which form of contraception is noted for having the lowest failure rate during typical use?

The subdermal progestin implant is noted for having the lowest failure rate during typical use among the listed contraception options. This is primarily due to its mode of action and long-lasting effectiveness. The implant is a small rod inserted under the skin of the upper arm, releasing a steady, low dose of progestin over several years, typically up to three to five years, depending on the specific formulation.

Because it is a long-acting reversible contraceptive (LARC), the implant offers a high level of effectiveness without the need for daily attention or adherence that many other forms of contraception require. Its mechanism provides continuous release of hormones, which significantly reduces the chance of pregnancy by inhibiting ovulation, thickening cervical mucus, and thinning the endometrial lining, thereby preventing fertilization and implantation.

In contrast, combined oral contraceptives and the progestin-only "mini-pill" require meticulous daily adherence for effective prevention of pregnancy. Depot medroxyprogesterone acetate injection, while also effective, requires repeat injections every three months, which can lead to lapses in protection if the schedule is not followed. These factors contribute to relatively higher failure rates in typical use of those methods compared to the implant's durable and consistent efficacy.