Medical Q&As

Conception - date it happened?

If baby is due on the 14th May when did conception take place?

The calculation of the expected date of delivery is based on the date of the first day of the last menstrual period. Working backwards from the date you have given that would indicate that the first day of the last menstrual period before conception took place was the 7th August 2002. Moving forward from that date we cannot say precisely when conception took place because that depends on the date on which ovulation took place. The other variable is the date or dates on which intercourse took place around the time of ovulation. If we simply assume for the purpose of this exercise that you had a 28 day cycle and that you ovulated in the middle of that cycle on day 14 we can then conclude that conception took place on or around the 21st August 2002. This date would move further on depending on the average length of your menstrual cycle. For example if your average cycle was 30 days the conception could have taken place in or around the 23rd August. However, it is important to realise that the calculations I have given are crude approximations and we do not have precise models for calculating retrospectively the precise date of conception. My best guess is that conception took place sometime around the third week in August 2002, approximately!