How can I determine my due date

A pregnancy generally lasts for 40 weeks from first day of your last menstrual period, or 38 weeks from conception.  If you know the date of your last menstrual period, or the date of conception (some women do!), and your cycles are regular, you should be able to determine your due date sitting at home. 

Based on LMP:
If your cycles are regular and 28 days long, then you can determine your due date by adding 9 months and 7 days to the first day of your last menstrual period (LMP).  For example, if your LMP began on September 5, then your expected due date (EDD) would be June 12 of the following year.

Based on date of Conception:
If your cycles are 28 days long and you know your date of conception, you can determine your due date by first subtracting 7 days, and then adding 9 months. However, this method will probably not work for most women unless they have had intercourse only once during the fertile period of that cycle and remember the date.
 
How does the doctor determine my due date

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