Expert: Catherine Beier MS CBE - 3/12/2008

Question
i really hope you can help me with this.... ok well im quite positive that my last period was from aug. 27 to sep. 1 i dont have a regular cycle so i never keep up with it... now my due date is june 2 i dont keep up with the dates that i have sex because i have a regular sexual partner but i had an enounter with one other person  i think during the month of august so can you please tell me the day i got pregnant and when i wouldve had sex???

Answer
Jasmine,

It can be difficult to actually determine a probable conception date when you have irregular cycles because your ovulation day will vary from month to month.

It will also be very difficult to tell when you had intercourse since sperm can live for 3-5 days in fertile cervical mucous.  This means that you could have had intercourse several days before you actually ovulated and conception occurred.

I checked your dates with the due date calculator located at http://www.givingbirthnaturally.com/calculating-due-date.html  It gave a due date of 6-2-08 with a probable conception date of 9-10-07.

However, this is based on the first day of your last period.  I'm guessing that this is how your due date was calculated rather than by early ultrasound.  Unfortunately, using the first day of your last period (LMP) much less accurate than an ultrasound between 8-10 weeks.  

This is because the LMP method assumes you have a perfectly regular 28 day cycle and always ovulate on day 14.  Since this is not the case for almost all women, a due date determined this way is a guess-estimate at best.

So, based on the due date you gave and assuming it is accurate, you most likely conceived around 9-10-07.  This could mean you had intercourse between 9-5-07 to 9-10-07.

These are rough estimates if your LMP was determined to calculate your due date.  If it was determined by early ultrasound, then they should be pretty close to the truth.


Best,
Catherine