Hormonal contraception
Mechanism of action for hormonal contraceptives
- Estrogen: suppresses release of GnRH from the hypothalamus → ↓ release of pituitary gonadotropins (FSH, LH)
- Decreased FSH → prevents ovarian folliculogenesis
- Decreased LH → inhibition of ovulation
- Progestin: synthetic progesterone →
- Inhibits GnRH and LH secretion → suppressed ovulation (main contraceptive mechanism)
- Inhibits endometrial proliferation → decreases chance of embryo implantation
- Changes cervical mucus (↓ volume and ↑ viscosity) and impairs fallopian tube peristalsis → inhibits sperm migration and embryo implantation
Contraindications
- ↑ Venous thromboembolism risk
- Tobacco use
- Prolonged immobilization
- Prior venous thromboembolism
- Thrombophilia (eg, antiphospholipid antibody syndrome) <3 weeks postpartum
- ↑ Cardiovascular disease & stroke
- Medical conditions negatively affected by ↑ estrogen
- Active breast cancer
- Active liver disease (eg, acute hepatitis, liver cancer)