A nurse is educating a client about the mechanism of action of Combined Oral Contraceptives (COCs). Which of the following is the primary way COCs prevent pregnancy?

Long-acting reversible contraceptives (LARCs)include intrauterine devices (IUDs) and subdermal implants. They provide extended contraceptionwithout user action, lasting from 3 to 10 yearsdepending on type. They are highly effective, with failure rates <1%, and are reversibleupon removal, allowing rapid return to fertility. LARCs do not protect against STIs, and barrier methods are still required. They are suitable for adolescents, with no age restrictions. Normal menstrual cycle length is 21–35 days; LARCs may alter bleeding patterns but do not affect systemic hormone levels significantly.

Rationale for correct answers

1.LARCs have efficacy >99%, with failure rates <1% per year. This is due to minimal user dependency and continuous hormone or copper release. Their effectiveness surpasses that of pills, patches, or rings.

3.LARCs are reversible upon removal. Fertility typically returns within days to weeks. This reversibility distinguishes them from permanent methods like sterilization.

5.LARCs are suitable for adolescents. They are safe, effective, and recommended by major guidelines including ACOG and WHO. They reduce unintended pregnancy rates in this population.

Rationale for incorrect answers

2.LARCs do not require daily adherence. This is a major advantage over oral contraceptives, which have typical-use failure rates of 7% due to missed doses. LARCs eliminate user error.

4.LARCs do not protect against STIs. They prevent pregnancy but offer no barrier to pathogens. Condoms remain necessary for STI prevention, especially in high-risk populations.

Take home points

• LARCs are >99% effective and user-independent.
• They are reversible and fertility returns quickly after removal.
• Adolescents can safely use LARCs.
• LARCs do not protect against STIs; condoms are still needed.

Depot medroxyprogesterone acetate (DMPA)is a progestin-only injectable contraceptiveadministered every 12 weeks. It suppresses ovulation, thickens cervical mucus, and thins the endometrium. Common side effects include weight gain, irregular bleeding, and bone mineral density lossdue to hypoestrogenic effects. DMPA delays return to fertility by 9 to 10 monthson average. It is safe during lactation, but does not increase milk supply. Normal bone mineral density (BMD) T-score is ≥−1.0; prolonged DMPA use may reduce BMD, especially in adolescents.

Rationale for correct answers

1.Weight gain is a documented side effect of DMPA, with average increases of 2–4 kg in the first year. It is attributed to increased appetite and fluid retention.

3.DMPA can reduce bone mineral density due to suppression of estrogen. This effect is reversible upon discontinuation but is significant in long-term use, especially in adolescents.

5.Irregular bleeding is common, especially in the first 6–12 months. It results from endometrial thinning and unpredictable shedding. Amenorrhea may develop with continued use.

Rationale for incorrect answers

2.DMPA does not result in immediate return to fertility. Ovulation may be delayed for 9–10 months after the last injection. This is due to prolonged suppression of the hypothalamic-pituitary-ovarian axis.

4.DMPA is compatible with breastfeeding but does not increase milk supply. It does not contain estrogen, which can suppress lactation, but its progestin component does not stimulate milk production.

Take home points

• DMPA causes weight gain, irregular bleeding, and potential bone density loss.
• Fertility return is delayed after discontinuation.
• Safe during lactation but does not enhance milk supply.
• Long-term use requires monitoring of bone health.