Contraception Mechanics.
Evaluating birth control requires looking at the delta between clinical trials (perfect use) and human behavior (typical use).
Hormonal vs Non-Hormonal
Hormonal methods generally work by suppressing ovulation, thickening cervical mucus to block sperm, and thinning the uterine lining.
Non-hormonal methods rely on physical barriers (condoms, diaphragms), chemical spermicides, or localized inflammation (Copper IUD) to prevent fertilization.
The Pearl Index
Efficacy is measured by the Pearl Index: the number of pregnancies per 100 women using a method for one year. A typical use failure rate of 7% means 7 out of 100 people using that method will get pregnant in a year.
Interactive Filter: Compare Methods
Hormonal IUD
Releases progestin locally.
Copper IUD
Creates an inflammatory response toxic to sperm.
Combination Pill
Estrogen & progestin. Taken daily.
External Condom
Latex or polyurethane barrier.
Common Mistakes & FAQs
Antibiotics and The Pill
Only Rifampin (used for tuberculosis) has proven clinically significant interaction. Common antibiotics for UTIs or strep throat do not lower the efficacy of the pill.
Oil-based lubes and condoms
Using Vaseline or lotion with latex condoms destroys the latex structure within seconds. Always use water-based or silicone-based lubricants with latex.
Plan B weight limit
Levonorgestrel (Plan B) begins to lose efficacy for individuals over 155 lbs. A copper IUD is the most effective emergency contraception regardless of weight.
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