Ovulation is the release of an egg from the ovaries.1 A woman is born with all her eggs. Once you start your periods, one egg (occasionally two) develops and is released during each menstrual cycle.2




After ovulation, the egg lives for approximately 24 hours3




Once the egg is released from the ovary it travels down the fallopian tube towards the womb. Fertilisation happens if a man’s sperm meets and fuses with the egg.1 Sperm can survive in the fallopian tubes for up to five days after sex.3




If the egg is not fertilised, the egg is reabsorbed into the body. Hormone levels fall, and the womb lining comes away and leaves the body as a period.1,2






A woman cannot get pregnant if ovulation does not occur.


1. Royal College of Obstetricians and Gynaecologists website. Medical terms explained. Available at http://www.rcog.org.uk/womens-health/patient-information/medical-terms-explained. Last accessed September 2013.

2. Aitken J et al. J. Clin. Invest 2008; 118 (4): 1330–1343.

3. Pallone S and Bergus G. J Am Board Fam Med 2009; 22: 147–157.

4. ellaOne® Summary of Product Characteristics.

5. World Health Organization. (In association with the International Consortium for Emergency Contraception, International Federation of Gynaecology and Obstetrics, International Planned Parenthood Federation, Department of Reproductive Health and Research). Fact sheet on the safety of levonorgestrel-alone emergency contraceptive pills. Available at: http://whqlibdoc.who.int/hq/2010/WHO_RHR_HRP_10.06_eng.pdf Accessed November 2013.