Expert: Dr. Harriet Johnson - 11/2/2009

Question
Hi Dr Johnson,
My periods are irregular, usually every 35-37 days. My last known period was on 6/29/09, that was on a 43 day cycle, which hasn't been the norm for me in about a year. I think I had a period at the beginning of Aug but it was strange, brown blood and only lasted abt 2 1/2days but for some reason, I didn't mark this down. I had an ultrasound on 10/8/09 and it said I was 9wks and 3 days. They gave me a due date of 5/10/10. Based on this information and me not knowing when my last period was, when do you think I got pregnant and how accurate are early ultrasounds? Could I have been further along? Do you think I could have gotten pregnant before the 12th of Aug? The reason I ask is because i had sex on Aug 6th with my now ex boyfriend. The following week, my ex husband and i decided we would give it another try and we have been together ever since Aug 14th. All the websits and others I have asked said i got pregnant aroung Aug 17th. We still plan on doing a DNA test but I have been stressing over this. Also I was thinking my doctor was using the 28 day cycle method, which I haven't had a 28 day cycle since 2006.

Answer
Hi Evita,

Early ultrasounds are very accurate as they measure the embryo which predicts how far along you are, they're rarely wrong, maybe a day or two but not weeks. From your 6/29/09 period I think you conceived around 7/28/09, the strange bleeding you had in early August was most likely implantation bleeding.