The hormone releasing IUDs function by-

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

Option (1) Make the cervix unsuitable for implantation and the uterus hostile to the sperms — Incorrect. The two organs are reversed. Implantation takes place in the uterus, not in the cervix, so it is the uterus that is made unsuitable for implantation.

Option (2) Make the uterus unsuitable for fertilization and the cervix hostile to the sperms — Incorrect. Fertilisation does not take place in the uterus; it takes place in the ampullary region of the fallopian tube. The uterus is where the embryo implants.

Option (3) Make the fallopian tube unsuitable for fertilization and the cervix hostile to the sperms — Incorrect. An IUD sits in the uterus and does not act on the fallopian tube.

Option (4) Make the uterus unsuitable for implantation and the cervix hostile to the sperms — Correct. The hormones stop the embryo from implanting in the uterus and make the cervical mucus hostile, so sperms cannot pass through.

Note: A similar question was also asked in CUET (UG) 2025 on 20-05-2025 (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.”