Timing of emergency IUD fitting.

We wish to thank Dr Davies for raising an issue we were not able to address in our original letter due to space limitations. The issue with emergency contraception intrauterine devices (EC IUDs) is slightly different. An EC IUD has to be fitted prior to implantation. This is a process that starts no sooner than 6 days after fertilisation, and fertilisation cannot happen prior to sexual intercourse. So, if all the risks are within 120 hours the IUD can always be considered regardless of where the woman may be in her cycle. Any risks more than 3 weeks ago warrant a pregnancy test, which will give a clear result. For risks between 3 weeks and 120 hours the date of the last normal Letters to the editor