The hormone releasing IUDs function by:

The correct answer is Option (4) → Making the uterus unsuitable for implantation and the cervix hostile to the sperms

IUDs work by increasing phagocytosis of sperms in the uterus; copper IUDs also release Cu ions that weaken sperm motility. Hormone releasing IUDs (Progestasert, LNG-20) do something more.

Option (1) Decreasing phagocytosis of sperms within the uterus — Incorrect. IUDs increase phagocytosis of sperms; the option states the effect backwards.

Option (2) Activating sperm motility and the fertilising capacity of sperms — Incorrect. The Cu ions of copper IUDs suppress sperm motility and fertilising capacity; no IUD activates them.

Option (3) Making the uterus suitable for implantation and the cervix hostile to the sperms — Incorrect. A contraceptive makes the uterus unsuitable for implantation, not suitable.

Option (4) Making the uterus unsuitable for implantation and the cervix hostile to the sperms — Correct. This is the extra action of hormone releasing IUDs such as LNG-20 and Progestasert, besides the action that all IUDs share.

Note: A similar question was also asked in CUET (UG) 2025 on 30-05-2025 (Slot 1).

NCERT Extract:
Population Stabilisation and Birth Control – “… Another effective and popular method is the use of Intra Uterine Devices (IUDs). These devices are inserted by doctors or expert nurses in the uterus through vagina. These Intra Uterine Devices are presently available as the non-medicated IUDs (e.g., Lippes loop), copper releasing IUDs (CuT, Cu7, Multiload 375) and the hormone releasing IUDs (Progestasert, LNG-20) (Figure 3.2). IUDs increase phagocytosis of sperms within the uterus and the Cu ions released suppress sperm motility and the fertilising capacity of sperms. The hormone releasing IUDs, in addition, make the uterus unsuitable for implantation and the cervix hostile to the sperms.”