Pregnancy Timeline: Calculating Your Due Date

Question
my last menstrual cyclye was on the 24 feb 09 , and usually have 29/30 day cycle so was given the due date of 3rd of dec on the 18 of may i had a scan, which i should have been 11 weeks and six days, but she gave me 11 weeks and two days, which would make my due date 5th of december, when about in march would i have got pregant, and which date is more accurate ? thanx

Answer
Debi,

In either case, due dates are generally not changed unless they are found to be more than two weeks different.  The further you get into pregnancy, the more ultrasound can be off, by as much as two weeks in either direction.  4 days is nothing to worry about, especially if the first date given was determined by your last period, not an ultrasound.  

Both dates are very close, meaning you conceived between the 10-14th of March.




Best,
Catherine