Mechanism of action of Intrauterine contraceptive devices: IUCDs act by inducing biochemical and histological changes in the endometrium there by preventing implantation.
They also prevent implantation through enzymatic reaction, by increasing tubal motility and by impairing sperm motility. Hormonal IUCDs : they act by forming thick cervical mucus, there by preventing entry of sperms.
By creating anovulation and by leading to insufficient luteal phase.
Division of IUCDs according to pregnancy rates(failure of contraception) (WHO-1987):
Group I : pregnancy rate > 2/100 women years, Eg. lippes loop, Cu 7, Cu T 200.
Group II : pregnancy rate <2 & >1/100 women years, Eg. Nova T, ML Cu 250, CuT220.
Group III : pregnancy rate <1/100 women years, Eg. Cu T380A, Cu T380S, ML Cu 375, LNG 20.
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