From ovulation, to fertilisation, to pregnancy

Since a woman can never know when she has ovulated, working out the exact point of fertilisation is also impossible. What we do know is that implantation occurs 6-12 days after fertilisation.1 Once implantation is complete, pregnancy is established.


Pregnancy begins when a fertilised egg has been implanted in the wall of a woman’s uterus. This definition is critical to distinguishing between a contraceptive that prevents pregnancy and an abortifacient that terminates it. 2,3

When women have unprotected intercourse, they are not immediately pregnant. Pregnancy can only occur a minimum of 6 days after intercourse (when a fertilised egg implants in the uterus).

Many women don’t understand when pregnancy begins. They believe it starts the moment they had UPSI. Within 5 days of UPSI a woman cannot be pregnant from that UPSI, because implantation cannot yet have occurred. But this mistaken understanding means that they can feel guilty about using EC because they wrongly believe it to be a form of abortion.4



1.Wilcox AJ et al. NEJM 1999; 340(23): 1796-1799.

2.Gold RB. The Guttmacher Report on Public Policy 2005. Available at Accessed June 2013.

3.Faculty of Sexual and Reproductive Healthcare. Guideline on Emergency contraception 2012. Available at Accessed June 2013.

4.Use of and attitudes towards emergency contraception: A survey of women in five European countries. Rossella E. Nappi, Paloma Lobo Abascal, Diana Mansour, Thomas Rabe, Raha Shojai and for the Emergency Contraception Study Group.