**Core Concept**
DMPA (Depot Medroxyprogesterone Acetate) is a long-acting reversible contraceptive injectable that provides effective contraception for an extended period. It works by suppressing ovulation and thickening cervical mucus, making it difficult for sperm to reach the egg.

**Why the Correct Answer is Right**
DMPA is administered once every 12 weeks (3 months) to maintain contraceptive efficacy. This long-acting formulation allows for convenient administration and high patient compliance. The medroxyprogesterone acetate in DMPA binds to progesterone receptors in the uterus, hypothalamus, and pituitary gland, thereby suppressing the secretion of gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH), which in turn inhibits ovulation.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because DMPA is not administered every 4 weeks.
**Option B:** Incorrect because DMPA is not administered every 6 weeks.
**Option C:** Incorrect because DMPA is not administered every 8 weeks.
**Option D:** Incorrect because the frequency of administration is not every 2 weeks.

**Clinical Pearl / High-Yield Fact**
Remember that DMPA can take up to 6 months to reach its full contraceptive efficacy, and its use is associated with a decrease in menstrual bleeding and an increase in bone density.

**Correct Answer: C. 3 months