text: why can't women take emergency pills after 52 hours of unprotected contact? well, i know this should have been in the pregnancy category, but this may involve more moral issues than it seems. i'm a volunteer at a family planning org. in a country where abortion is illegal, and i've asked this question but the answers so far have been varied, which makes it confusing. surely its more to do with the effectiveness of the pill. in britain you can take it upto 72 hours later, but if you wait that long its only 50% as likely to prevent pregnancy than if you take it straight away.  i think its more to do with the fact that the longer you leave it, the more likely it is that the embryo will have planted itself in the uterine lining, and that the body will have signalled the release of progesterone - the pregnancy hormone. after this time, you are pregnant, and only a much stronger pill that will cuase contractions of the unterus to dispell the embryo, will work.