Postcoital birth control pills…. Ovarian hormones (estrogen) taken in large doses within 72
hours after sexual intercourse usually prevent implantation of the blastocyst, probably by
altering tubal motility, interfering with corpus luteum function, or causing abnormal changes
in the endometrium. These hormones prevent implantation, not fertilization.
Consequently, they should not be called contraceptive pills. Conception occurs but the
blastocyst does not implant. It would be more appropriate to call them "contraimplantation
pills." Because the term abortion refers to a premature stoppage of a pregnancy, the term
abortion could be applied to such an early termination of pregnancy.

Research has shown that, in a laboratory setting, sperm can migrate into the Fallopian tube, the site
of fertilization, within five minutes of intercourse.(1) Thus, the use of any form of emergency birth
control ‘the next morning’ would be many hours too late for any purported anti-sperm activity.(2)

Research that is more recent has demonstrated that, under the influence of uterine contractions, rapid
transport of sperm-sized spheres to the Fallopian tube can take only one minute.(3)

Once the sperms have reached the site of fertilisation, all that remains, is for the oocyte to be present.
If conception is going to occur, it will, irrespective of any hormonal manipulation. Oocytes are usually
fertilised within 12 hours of ovulation, and are viable for about 24 hours of ovulation. For fertilisation to
occur, ovulation has usually occurred prior to intercourse, but can occur after intercourse.

Thus the action of the MAP is normally to prevent implantation rather than to prevent fertilisation, and
therefore, by definition, the MAP is not a contraceptive but an abortifacient.