Biology · Reproductive Health · NEET
Copper ions released by the IUD are toxic to sperm. They suppress sperm motility and reduce the sperm's fertilising capacity, so sperm cannot reach or fertilise the egg. This is why copper IUDs are non-hormonal. Remember: copper attacks the sperm, it does not stop ovulation.
Oral pills (progestogen or progestogen-estrogen combinations) mainly inhibit or prevent ovulation. If no egg is released, fertilisation cannot happen. They also slow implantation and change the cervical mucus to retard sperm entry. So the PRIMARY mechanism NCERT expects is: they inhibit ovulation and implantation and alter cervical mucus.
Saheli is a non-steroidal oral pill (contains centchroman), taken once a week. Being non-steroidal, it has very few side effects and high contraceptive value. Regular pills are steroidal (hormonal). The exam point: Saheli = non-steroidal, once a week, developed by CDRI Lucknow.
Hormone-releasing IUDs make the uterus unsuitable for implantation and make the cervix hostile to sperm by thickening cervical mucus. Non-medicated IUDs (Lippes loop) increase phagocytosis of sperm in the uterus. So different IUD types use different mechanisms even though all sit inside the uterus.
In vasectomy a small part of the vas deferens is cut and tied, so sperm cannot pass out into the semen. Sperm are still produced but never reach the ejaculate. In tubectomy the fallopian tubes are cut/tied so the egg cannot travel down and sperm cannot reach it. Both block the transport pathway, not production.
A condom (barrier method) physically prevents the sperm from meeting the egg by stopping sperm entry into the female tract. It blocks the MEETING step. Bonus for NEET: condoms also protect against STIs and AIDS, which pills and IUDs do not.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Oral pills act by three mechanisms: they inhibit ovulation, alter cervical mucus to block sperm entry, and slow implantation. Hormone-releasing IUDs also act in two ways: unsuitable uterus for implantation and hostile cervix.
Copper-releasing IUDs suppress sperm motility and fertilising capacity with copper ions. Non-medicated IUDs increase phagocytosis of sperm inside the uterus.
Surgical methods (sterilisation): vasectomy cuts the vas deferens so sperm cannot leave, and tubectomy cuts the fallopian tube so the egg and sperm cannot meet.
Yes, largely. Injectables and implants use progestogens (with or without estrogen). Their main effect is inhibiting ovulation, plus altering cervical mucus and making implantation difficult, just like oral pills but longer lasting.
Only the condom (a barrier method) protects against sexually transmitted infections and AIDS, in addition to preventing pregnancy. This is a favourite NEET one-liner.
