Contraception Methods

Contraception comprises medical and barrier methods designed to prevent unintended pregnancy by interfering with fertilization, implantation, or ovulation. With approximately 85% of reproductive-age women using contraception at some point and unintended pregnancies accounting for ~45% of all pregnancies in the United States, contraceptive counseling is a fundamental clinical competency. The choice of contraceptive method involves balancing efficacy (measured as typical-use and perfect-use failure rates), safety profile, side effects, return to fertility, cost, and individual patient factors including cardiovascular risk, thromboembolism risk, and preference for user-dependent versus long-acting methods. Understanding the molecular mechanisms, comparative efficacy, absolute and relative contraindications, and management of side effects is essential for boards and clinical practice. Modern contraception extends beyond pregnancy prevention to include management of menstrual disorders, endometriosis, and acne, making contraceptive knowledge integral to gynecologic practice.

Contraceptive methods interrupt the reproductive cycle at multiple anatomical and biochemical levels. Understanding these mechanisms is essential for predicting efficacy and managing side effects.

The HPO axis is regulated by gonadotropin-releasing hormone (GnRH) secreted from the hypothalamus in a pulsatile fashion. This stimulates the anterior pituitary to secrete follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which drive follicular development and ovulation. Combined oral contraceptives (COCs) containing ethinyl estradiol (EE) or newer estrogens (estradiol valerate, estradiol) and progestins (norgestimate, levonorgestrel, desogestrel, drospirenone, dienogest) suppress GnRH secretion through negative feedback at the hypothalamus and anterior pituitary. Estrogens inhibit FSH secretion preferentially, preventing follicular recruitment, while progestins suppress LH surge—the critical trigger for ovulation. The estrogen component also stabilizes endometrial proliferation and reduces breakthrough bleeding. At typical doses, ovulation is suppressed in >99% of cycles. Progestin-only pills (POPs) contain only 0.3-0.75 mg of progestin; their mechanism relies primarily on cervical mucus thickening (creating a hostile environment for sperm penetration) and secondary effects on the endometrium and tubal transport. POPs do not consistently suppress ovulation at standard doses, accounting for their slightly lower efficacy compared to COCs.

Progestins increase cervical mucus viscosity and reduce spinnbarkeit (the ability to stretch and form ferning crystalline patterns characteristic of estrogen-dominant mucus). Progestin-releasing intrauterine devices (IUDs), particularly the levonorgestrel IUD, release progestin directly into the endometrial cavity and systemic circulation (though primarily local effect), thickening and reducing volume of cervical mucus. This creates a mechanical and biochemical barrier to sperm ascension through the cervix and fallopian tubes. The increased mucus viscosity prevents the forward motility essential for sperm navigation. This mechanism explains why cervical mucus monitoring during POPs or progestin-releasing IUDs can demonstrate altered characteristics. Barrier methods (condoms, diaphragms) work by purely mechanical means, physically preventing sperm deposition in the upper genital tract.

Both estrogens and progestins alter endometrial morphology and receptivity. Progestins transform the proliferative endometrium into a secretory state through progesterone receptor (PR) activation. The normal secretory changes include glycogen accumulation, glandular tortuosity, and increased vascularity—but these are attenuated by exogenous progestins in contraceptive doses, resulting in endometrial atrophy. Copper IUDs induce a sterile inflammatory response with recruitment of polymorphonuclear leukocytes and macrophages into the endometrial cavity, creating a hostile environment toxic to sperm and potentially embryonic tissue. The copper also impairs sperm motility directly. Levonorgestrel IUDs combine this inflammatory effect with progestin-induced endometrial atrophy and thinning—the endometrium may become <1 mm thick. This endometrial suppression is highly effective at preventing implantation, should fertilization occur, making IUDs among the most effective contraceptives.

In this context, "etiology" refers to the indications for and factors influencing choice of contraceptive method.

All reproductive-age individuals engaging in heterosexual intercourse are potential candidates for contraception. Baseline efficacy varies dramatically: intrauterine devices (copper or levonorgestrel) have typical-use failure rates of 0.2-0.8% per year, contraceptive implants (subdermal rod releasing etonogestrel) have <0.05% failure rates, COCs have typical-use failure rates of ~7-9% (perfect use 0.3%), and barrier methods have typical-use failure rates of 18% for condoms. User-dependent methods account for most failures in typical use, making the distinction between perfect and typical use clinically relevant when counseling patients.

Certain conditions dramatically increase risk of venous thromboembolism (VTE), myocardial infarction (MI), or stroke with estrogen exposure: current or history of VTE or pulmonary embolism, thrombophilia (Factor V Leiden, prothrombin G20210A, protein C/S deficiency), migraine with aura (increased stroke risk), age >35 years with smoking, uncontrolled hypertension (≥160/100 mmHg), major surgery with immobilization, known coronary artery disease or cerebrovascular disease, and current breast cancer. These patients require progestin-only methods (IUD, implant, POP) or non-hormonal methods (copper IUD, barrier methods, lactational amenorrhea).

Breastfeeding: Estrogen-containing contraceptives can reduce milk supply and are traditionally avoided for at least 6 months postpartum; progestin-only methods are safe. Heavy or prolonged menses: Levonorgestrel IUDs significantly reduce or eliminate menstrual bleeding (up to 50% become amenorrheic), making them ideal. Dysmenorrhea and endometriosis: Both COCs (through continuous or extended-cycle use) and progestin-only methods provide relief. Acne or hirsutism: COCs with antiandrogenic progestins (drospirenone, cyproterone acetate) or lower-androgenicity formulations benefit these patients. Age and smoking: Women ≥35 years who smoke should avoid estrogen; those <35 without other VTE risk factors can use estrogen-containing methods if counseled on cessation.

Enzyme-inducing antiepileptic drugs (phenytoin, carbamazepine, barbiturates, phenobarbital) and rifamycins (rifampicin/rifampin) induce CYP3A4 metabolism of ethinyl estradiol and progestins, reducing contraceptive efficacy. These patients require higher-dose estrogen formulations or non-hormonal/IUD methods. Antiretroviral protease inhibitors (ritonavir) and some newer drugs (dolutegravir with some progestins) have bidirectional interactions requiring counseling.

This section addresses the clinical presentations related to contraceptive use—both intended effects and side effects.

The menstrual cycle is profoundly affected by hormonal contraceptives. COCs typically produce shortened, lighter menses (often 3-4 days) due to reduced endometrial proliferation. Extended-cycle COCs (84 active pills + 7 placebo) or continuous regimens (all active pills with no placebo week) can produce amenorrhea or very light spotting, which patients may find appealing or concerning depending on preference. Levonorgestrel IUDs cause progressive amenorrhea in ~50% of users by 12 months, with the remainder experiencing light spotting or scanty periods. Copper IUDs characteristically increase menstrual volume and duration by 20-50%, which is the primary reason for discontinuation; this is due to increased uterine prostaglandin production. POPs produce variable bleeding: while the traditional belief is that POPs are associated with less bleeding than COCs, actual patterns vary from amenorrhea to frequent spotting.

This occurs in 10-30% of users in the first 3 months of COC use and typically resolves as the endometrium stabilizes. Breakthrough bleeding is more common with progestin-only formulations and with extended-cycle or continuous regimens during the first several cycles. The mechanism involves inadequate endometrial stabilization by the lower progestin doses used in modern formulations. Management includes reassurance that it usually resolves, consideration of switching to a higher-dose formulation or adding supplemental estrogen temporarily, or ensuring consistent pill-taking behavior (missed pills are the most common cause).

Nausea affects 10-20% of women starting COCs, particularly those containing higher estrogen doses; it typically improves by the 3rd cycle as tolerance develops. The mechanism involves direct central nervous system effects of estrogen and gastric slowing. Breast tenderness (mastalgia) results from estrogen-induced proliferation of breast tissue and is generally mild and self-limited. Mood changes including depression, anxiety, or irritability occur in 5-10% of users; while small and mechanistically unclear, they may relate to estrogen effects on serotonin and GABA systems. The levonorgestrel-containing formulations appear to carry a higher risk of mood changes than other progestins in observational data, though causality remains debated. These symptoms usually resolve within 3-6 months; if persistent, switching to a different progestin type or dose is warranted.

Estrogens promote sodium retention through increased aldosterone sensitivity; fluid retention may manifest as bloating, weight gain (typically 1-3 lbs), and increased blood pressure. Drospirenone, a spironolactone analog progestin, is antiandrogenic and also has antimineralocorticoid activity, reducing sodium retention. Progestins with more androgenic activity (levonorgestrel) cause less fluid retention but may increase appetite. Weight gain >5% of baseline occurs in 10-15% of users; whether this is true metabolic changes or altered appetite is debated. Counseling patients that initial weight gain often plateaus and can be managed with exercise and dietary awareness is important.

Estrogens increase hepatic synthesis of angiotensinogen, thereby activating the renin-angiotensin-aldosterone system (RAAS). Blood pressure increases by 5-10 mmHg on average in COC users; 5-10% develop clinically significant hypertension. This effect is more pronounced with higher-dose estrogen formulations and in older women (>35 years). Baseline blood pressure should be measured before initiating COCs; monitoring every 3-6 months is appropriate.

Unlike infections associated with other foreign bodies, IUD placement does not produce local inflammatory signs at insertion or during routine use. The endometrial inflammatory response to copper IUDs is sterile (no bacteria present); acute infection at insertion is rare (<0.1% with proper aseptic technique). Pelvic inflammatory disease (PID) risk is not increased with IUDs in monogamous women, though risk may be slightly elevated if untreated gonorrhea or chlamydia is present at insertion.

Levonorgestrel, norgestimate, and norethindrone (older progestins) have weak androgenic activity. Women using these formulations may experience acne, hirsutism, or male-pattern hair loss. Drospirenone, cyproterone acetate, and dienogest are antiandrogenic, actually improving acne and hirsutism. This distinction is critical when counseling patients with polycystic ovary syndrome (PCOS) or those concerned about androgenic effects.

Some users intentionally use COCs or progestin-only methods continuously (omitting placebo weeks) to eliminate menses, which many find desirable. This is safe and effective; amenorrhea rates of 70-90% can be achieved with extended-cycle formulations. However, breakthrough bleeding occurs in 20-30% during the first year. Patients should be counseled that this is intentional and expected, distinguishing it from unplanned amenorrhea (which could indicate pregnancy, ovarian failure, or other pathology).

Contraceptive "diagnosis" refers to the assessment process for selecting appropriate contraceptive methods and identifying contraindications.

Essential elements include current pregnancy status (ruled out with urine or serum beta-hCG if any possibility), menstrual history (cycle length, duration, heaviness), obstetric history (parity, mode of delivery, history of ectopic pregnancy), gynecologic history (STI history, PID, cervical abnormalities), and prior contraceptive use (method, duration, reasons for discontinuation, side effects). Patients must be asked about absolute and relative contraindications: thromboembolic disease, migraine with aura, smoking status, blood pressure, and liver disease. The World Health Organization (WHO) Medical Eligibility Criteria for Contraceptive Use categorizes conditions into 4 categories: 1 (no restriction), 2 (advantages generally outweigh risks), 3 (risks generally outweigh advantages, method not recommended unless other options unavailable), and 4 (unacceptable health risk). This framework is essential for standardized assessment across diverse patient populations.

Blood pressure must be measured at baseline; hypertension ≥160/100 mmHg is a Category 3-4 contraindication for estrogen-containing methods. Smoking status is critical: women ≥35 years who smoke are Category 3-4 for COCs due to VTE and MI risk. Framingham Risk Score or similar cardiovascular risk calculators may guide decisions in older women. History of VTE, thrombophilia testing (in those with strong family history or recurrent VTE), presence of migraine with aura, and personal or family history of early MI or stroke should all be documented. D-dimer testing or thrombophilia screening is not routinely recommended before COC initiation in asymptomatic women but may be considered in those with strong family history (multiple relatives with VTE before age 50).

Active liver disease (acute hepatitis, cirrhosis, benign or malignant liver tumors) contraindicates estrogen-containing methods (Category 3-4). Mild liver disease (chronic hepatitis, well-compensated cirrhosis) is Category 2. Lipid panel is not routinely required before COC initiation in otherwise healthy women but should be obtained in those with family history of premature MI or stroke. Estrogens increase trigly

Step 1 — exclude pregnancy and screen for contraindications: CDC U.S. Selected Practice Recommendations (US SPR) allow initiation on any day ("Quick Start") if the clinician is reasonably certain the patient is not pregnant using the history checklist; a negative urine hCG alone is not required. Screen with the CDC U.S. Medical Eligibility Criteria (US MEC), the American adaptation of the WHO framework already described.

Step 2 — counsel by tiered efficacy (ACOG and CDC): present most-effective methods first, but let the patient choose; coercion toward LARC is an ethical error ACOG explicitly warns against.

Step 3 — match the method to the contraindication: estrogen-free options (LNG-IUD, implant, POP, DMPA, copper IUD) for migraine with aura, age ≥35 with smoking, prior VTE/thrombophilia, uncontrolled hypertension, and the first 21 days postpartum (US MEC category 4 for estrogen). Copper IUD is the answer when hormones are contraindicated altogether (e.g., current breast cancer).

Definitive management: bilateral salpingectomy is ACOG's preferred sterilization for permanent contraception given the ovarian-cancer risk reduction; vasectomy is safer, cheaper, and requires post-procedure semen analysis before relying on it.

Contraindicated: estrogen with prior VTE, aura migraine, or smoking at ≥35; IUD insertion with current purulent cervicitis, known gonorrhea/chlamydia, or unexplained vaginal bleeding.

Progestin-related: DMPA causes reversible bone mineral density loss and delayed return of fertility (up to ~10 months after the last injection); drospirenone can cause hyperkalemia in renal impairment or with ACE inhibitors/potassium-sparing diuretics; irregular bleeding is the leading cause of discontinuation for all progestin-only methods.