Emergency hormonal contraception EHC

Before ovulation it may prevent ovulation by delaying or inhibiting the release of the ovum from the ovary. 

After ovulation it may prevent fertilisation by affecting the motility of the fallopian tube and preventing sperm from meeting the ovum. 

After fertilisation it induces changes in the endometrium that render it unreceptive to the ovum and prevent implantation. 

95% effective if the first dose is taken within 24 hours 85% effective if used within 24-48 hours 58% effective if used within 48-72 hours. 

If two or more pills are missed from the last seven in a pack, EHC is not necessary providing that the next pack is started immediately, i.e. without the normal pill-free break, with a progestogen-only contraceptive  

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