Sex and birth control
How pregnancy happens, every birth control method and its trade-offs, emergency contraception, STIs and consent.
- 1How pregnancy happensPregnancy happens when sperm meets an egg, usually in a fallopian tube. Because sperm can live up to five days, sex up to five days before ovulation can lead to pregnancy, and that includes sex during a period.
- 2Birth control methods comparedThe implant and IUDs are the most effective reversible methods because there's nothing to remember. The pill, patch, ring and shot work well when used on time. Only condoms also protect against STIs, and no method harms future fertility.
- 3Emergency contraceptionEmergency contraception lowers the chance of pregnancy after unprotected sex. The copper IUD works best. The pills work by delaying ovulation, work better the sooner they're taken, and don't cause an abortion.
- 4STIsSTIs are very common and most cause no symptoms, so testing is the only way to know. Untreated chlamydia and gonorrhea can cause infertility. Condoms and the HPV vaccine protect, and a Pap test is not an STI test.
- 5ConsentConsent is a clear, freely given yes, every time, for every activity. It can be taken back at any moment. Silence, a past yes, or a body's physical response is not consent.
- 6For partners and loved onesBirth control, STI testing and consent are shared responsibilities. Know the facts, share the costs and the planning, and never pressure.
- QuizA short quiz on this section. Try again for new questions.
Where can I learn more?
- Cleveland Clinic: Sperm
- Cleveland Clinic: Fallopian tubes
- Physiology, Menstrual Cycle, StatPearls 2024
- Cleveland Clinic: Ovulation
- NHS: Periods and fertility in the menstrual cycle
- Cleveland Clinic: Can you get pregnant on your period?
- CDC: Contraception and birth control methods
- ACOG: Heavy menstrual bleeding
- ACOG: Abnormal uterine bleeding
- ACOG: Dysmenorrhea (painful periods)
- Return of fertility after discontinuation of contraception: a systematic review and meta-analysis, Contracept Reprod Med 2018
- Cleveland Clinic: Withdrawal bleeding
- ACOG: Emergency contraception
- NHS: Emergency contraception
- WHO: Sexually transmitted infections fact sheet (2025)
- CDC: About chlamydia
- CDC: STI treatment guidelines, HPV-associated cancers and precancers
- CDC: HPV vaccine
- RAINN: Consent 101