Contraception methods prevent unwanted pregnancy by different mechanisms. Natural methods: Periodic abstinence (rhythm/calendar method): avoid sex during fertile days (approximately days 10-17 of a 28-day cycle). Unreliable (requires regular cycles). Coitus interruptus (withdrawal): unreliable, does not prevent STIs. Lactational amenorrhoea: breastfeeding suppresses ovulation for up to 6 months postpartum. Barrier methods: physically prevent sperm from reaching egg. Male condom (latex): most widely used, also prevents STIs. Female condom (polyurethane). Diaphragm, cervical cap: used with spermicide. Hormonal methods: suppress ovulation and/or alter cervical mucus. IUDs: intrauterine devices. Surgical: permanent (vasectomy, tubectomy). Each method has different efficacy (measured by Pearl Index: pregnancies per 100 woman-years of use) and different side effect profiles.

IUDs are small devices placed inside the uterine cavity by a healthcare provider. First generation (non-medicated, inert): Lippes Loop — polyethylene loop, no longer widely used. Second generation (copper-releasing): CuT-380A (most widely used worldwide): T-shaped, 380 mm2 copper surface, lasts 10+ years. Multiload-375 (ML-375): T-shape with copper on arms and vertical stem, 375 mm2 copper. Nova-T: similar copper IUD. Mechanism of copper IUDs: copper ions are spermicidal (toxic to sperm, impair motility and function). Copper also prevents fertilisation and possibly implantation. No hormones — suitable for those who cannot use hormonal methods. Third generation (hormone-releasing): Progestasert: releases progesterone. Mirena/LNG-IUS: releases levonorgestrel (synthetic progestogen). Mechanism: thickens cervical mucus, thins endometrium, suppresses ovulation in some cycles. Used for contraception AND treatment of heavy menstrual bleeding, endometriosis.

Saheli (Chhaya, Centron) was developed by CDRI (Central Drug Research Institute), Lucknow, India. Active ingredient: centchroman (ormeloxifene) — a selective oestrogen receptor modulator (SERM). NOT a traditional hormonal pill (not oestrogen/progestin). Classification: oral contraceptive / non-steroidal anti-oestrogenic compound. Dosing: once weekly (unlike daily hormonal pills) — taken every week, making compliance easier. Mechanism: accelerates ovum transport through the fallopian tube → egg reaches uterus before endometrium is ready for implantation → implantation fails. Also: alters cervical mucus and endometrial lining. Advantages: no oestrogen → no risk of thrombosis, cardiovascular effects, nausea associated with oestrogen. Once weekly → better compliance. Highly effective (99%+ with correct use). Disadvantage: must be taken very regularly (even small delay affects efficacy). Specifically developed for Indian women to provide a safe, accessible, non-hormonal option.

COCP contains synthetic oestrogen (ethinylestradiol) and progestogen (levonorgestrel, norethisterone, desogestrel, etc.). Mechanism: Suppress ovulation (primary mechanism): oestrogen + progestogen suppress LH and FSH → no follicle development → no ovulation. Thicken cervical mucus: progestogen → mucus hostile to sperm. Thin endometrium: progestogen → poor implantation site (third line of defence). Standard regimens: 21 active pills then 7 pill-free days (withdrawal bleed). 28-day packs with 7 inactive/sugar pills (for continuous habit). Mini-pill (progestogen-only pill, POP): no oestrogen. Works mainly by cervical mucus thickening. Suitable for: breastfeeding mothers, women who cannot take oestrogen (hypertension, migraine with aura, thrombosis history). Taken daily without a break. Advantages of COCP: highly effective (>99%), regular predictable periods, reduced dysmenorrhoea, reduced risk of ovarian and endometrial cancer, treatment of PCOS and endometriosis. Risks: small increased risk of VTE (venous thromboembolism), stroke in women with migraine with aura, not suitable for smokers >35 years.

Male condom: most widely used barrier. Latex (or polyurethane/polyisoprene for latex allergy). Prevents both pregnancy and STIs (including HIV). Efficacy: 98% perfect use, 82% typical use. Free in many countries through public health programs. Female condom: polyurethane pouch inserted into vagina before intercourse. Covers inner vagina and external labia. Can be inserted up to 8 hours before intercourse. Less popular but gives woman control. Diaphragm: dome-shaped rubber/silicone cup with a flexible rim. Inserted before intercourse to cover the cervix. Must be used with spermicidal gel/cream for effectiveness. Must remain in place for 6 hours after intercourse. Requires fitting by healthcare provider. Cervical cap (FemCap): similar to diaphragm but smaller, fits over cervix more precisely. Sponge: foam sponge soaked in spermicide, placed over cervix. Spermicides alone: chemicals (nonoxynol-9) that destroy sperm. Low efficacy when used alone — mainly used with other methods.

Emergency contraception (EC) prevents pregnancy AFTER unprotected intercourse. NOT a routine contraceptive method. Options: Levonorgestrel EC (i-pill, Plan B, Nordette): progestogen-only pill. Most effective if taken within 72 hours (but can be used up to 120 hours). Mechanism: delays/inhibits ovulation. Prevents fertilisation. Does NOT cause abortion if already pregnant. Efficacy: 85-95% within 72 hours. Ulipristal acetate (EllaOne): selective progesterone receptor modulator. Effective up to 120 hours. Slightly more effective than levonorgestrel especially 72-120 hours. Copper IUD: most effective EC (>99%). Can be inserted up to 5 days after unprotected intercourse. Also provides ongoing contraception. Mechanism: copper ions impair sperm, prevent fertilisation, may prevent implantation. Mifepristone (RU-486): anti-progesterone. Used in some countries as EC and for medical abortion. Combined EC (Yuzpe method): high dose combined pills — less effective, more side effects.

Surgical sterilisation is the most effective permanent contraception method. Female sterilisation (tubectomy / tubal ligation): fallopian tubes cut, tied, cauterised, or blocked with clips/rings. Prevents egg from reaching uterus, prevents sperm from reaching egg. Done laparoscopically (minimally invasive). Highly effective (99.5%+). Reversal possible but with limited success. Male sterilisation (vasectomy): vas deferens cut and tied/cauterised under local anaesthetic. Prevents sperm from being included in ejaculate. Simpler, cheaper, safer than female sterilisation. Highly effective (99.9%+). Takes ~3 months for complete effect (sperm remaining in vas must clear). Reversal success: 50-70% (varies with time since procedure). These are the preferred methods for couples who have completed family. In India: national family planning programme promotes these as spacing/permanent methods.

STIs (Sexually Transmitted Infections), formerly called STDs (Sexually Transmitted Diseases), are infections transmitted through sexual contact. Common STIs: Bacterial: Gonorrhoea (Neisseria gonorrhoeae), Chlamydia (Chlamydia trachomatis) — most common STI, often asymptomatic. Syphilis (Treponema pallidum) — stages: primary (painless chancre), secondary (rash), tertiary (cardiovascular, neurological). Chlamydia and gonorrhoea cause PID (pelvic inflammatory disease) → infertility. Viral: HIV/AIDS. Herpes simplex virus (HSV-2 genital herpes). HPV (Human Papillomavirus) — causes genital warts AND cervical cancer. Hepatitis B and C. Parasitic: Trichomonas vaginalis (trichomoniasis). Candidiasis (thrush — fungal, not technically STI but sexually transmitted). Prevention: condoms most effective barrier. Vaccination: HPV vaccine (Gardasil, Cervarix — prevents cervical cancer), Hepatitis B vaccine. Treatment: bacterial STIs — antibiotics. Viral STIs — antivirals (not curable for HIV, herpes). Regular screening especially in high-risk individuals.