Suppresses LH surge, which is the primary trigger for ovulation.
Thickens cervical mucus, creating a barrier that prevents sperm penetration.
Thins the uterine endometrium, making it less suitable for implantation.
Progestin-only methods rely more heavily on thickening cervical mucus and thinning the endometrium, with ovulation inhibition being less consistent (especially with low-dose pills).
Types of Hormonal Contraception
Combined Hormonal Contraceptives (CHCs) - contain both estrogen and progestin.
Oral Contraceptive Pills (OCPs): Most common form, taken daily. Efficacy is >99% with perfect use, but closer to 91% with typical use.
Transdermal Patch: Applied weekly for 3 weeks, followed by a patch-free week.
Vaginal Ring: Inserted for 3 weeks, followed by a ring-free week.
Progestin-Only Contraceptives (POCs) - indicated for patients with contraindications to estrogen (e.g., smokers >35, history of VTE, migraine with aura).
Progestin-Only Pills (POPs or “minipill”): Must be taken at the same time each day due to lower hormone dose.
Injectable Contraception (e.g., Depo-Provera): Administered every 3 months. Associated with potential for delayed return to fertility and decreased bone mineral density with long-term use.
Subdermal Implant (e.g., Nexplanon): A small rod inserted in the upper arm, effective for 3 years. Highly effective (>99%) due to user independence.
Hormonal Intrauterine Device (IUD) (e.g., Mirena, Kyleena): T-shaped device placed in the uterus, effective for 5-8 years depending on the brand. Works primarily by local progestin effects on mucus and endometrium. Highly effective (>99%).
Key Side Effects & Adverse Events
Common Side Effects (often improve after 2-3 months):
Breakthrough bleeding/spotting (especially common with POPs and in the first few cycles of CHCs).
Headaches, nausea, breast tenderness, bloating.
Mood changes.
Serious Adverse Events (mainly associated with estrogen in CHCs):
Venous Thromboembolism (VTE): ↑ risk of DVT and PE. Risk is highest in women who smoke, are obese, or have thrombogenic mutations.
Hypertension: Estrogen can increase blood pressure.
Stroke & Myocardial Infarction: Risk is significantly elevated in women who smoke and are over age 35.
Hepatic Adenoma: A rare, benign liver tumor.
Gallbladder Disease: Increased risk of cholelithiasis.
Absolute Contraindications to Combined Hormonal Contraceptives
Hx of VTE (DVT/PE), stroke, or ischemic heart disease.
Smoker >35 years old (>15 cigarettes/day).
Severe/uncontrolled hypertension (>160/100 mmHg).
Migraine with aura (increased stroke risk).
Current breast cancer.
Active or severe liver disease (cirrhosis, liver tumor).
Known thrombogenic mutations (e.g., Factor V Leiden, Protein C/S deficiency).
<21 days postpartum due to increased VTE risk.
Non-Contraceptive Benefits (primarily CHCs)
Regulation of menstrual cycles, treatment for dysmenorrhea and menorrhagia.
Treatment for acne and hirsutism.
Management of symptoms related to PCOS and endometriosis.