Expert: Catherine Beier MS CBE - 1/5/2009

Question
my last menstruation date was on sept.23,2003..i would like to find out when is the exact date or an estimated date of when my baby was conceived...according to my ultrasound and my LMP im told that i'm 14wks and 6days..but my doctor tells me that i could almost be 16 to 17wks...my fiancee was incarcerated on the 20th of sept and was released on the 30th..so of course in the back of his mind he thinks i cheated but i know 100% i did no such thing..

so my question is..was my LMP the day my baby was conceived or was he conceived the week before? having the answer to this question would really put me and my fiancee out of stress..please email me or post ur answer..thank you

Answer
Esteph,

The conception date is never the same as your LMP date.  Conception occurs near the time of ovulation which is typically about 14 days before your next period is to begin.


Based on your LMP and your due date, you most likely conceived around the 6-8th of October, after your fiancee was released.


I'm unsure why your doctor thinks you may be approximately 1-2 weeks further along.  If he said you are measuring that far ahead, then he could have meant that you're measuring like you were that far along, while still being 15 weeks.


To be sure, ask your doctor why he thinks you could be further along or if he was just saying you're measuring big.



An early ultrasound (before 12 weeks, preferably between 8-10 weeks) is typically accurate within 3 days or less, so if you had your ultrasound at that point, it should be a very accurate estimate of your due date and would align correctly with your estimated conception.




Best,
Catherine