CuT delays pregnancy due to:

The correct answer is Option (3) → Increases the phagocytosis of sperms within the uterus

CuT is a copper-releasing intra-uterine device (IUD). It is placed in the uterus by a doctor and prevents pregnancy by acting on the sperms.

(1) Decrease in the level of progesterone — Incorrect. CuT is not a hormonal device and does not lower any hormone. Progesterone is needed to keep the uterus ready for a pregnancy.

(2) Inhibition of ovulation and implantation — Incorrect. Stopping ovulation is the way hormonal pills work. CuT does not stop ovulation. It acts on the sperms.

(3) Increases the phagocytosis of sperms within the uterus — Correct. IUDs increase phagocytosis (the engulfing and destroying) of sperms in the uterus. The Cu ions that are released also suppress the motility of sperms and their fertilising capacity. So fertilisation does not take place.

(4) Increase in the level of estrogen — Incorrect. CuT does not release estrogen and does not raise its level.

NCERT Extract:
Population Stabilisation and Birth Control – …