[KatiInCT]

I am hoping to pick the brains of some of our resident experts. I had assumed my EDD was July 1, 2009 based on my LMP and the fact that my ovulation was at a semi typical (2 week) CD15 mark. I had an early ultrasound done yesterday because of some bleeding I had last week and the CRL length corresponded to only 6 week 0 days with a due date of July 9, 2009 (instead of 7 weeks 2 days like I was expecting).

To my (untrained) eye it seems that if the sperm from the last BD (Oct 10th) included the special swimmer, he would have had to survive 6 days to make me 6 weeks 0 days (conception on or around Oct 16th for a 40 week gestation = July 9, 2009). Am I completely misunderstanding? Any input would be appreciated.

I had the same thing happen, I was sure I was due Sept. 10th and my first ultrasound showed Sept. 21st, then at 7 weeks it showed Sept. 18th, so that's what we went with. I ovulated later than I thought I guess. You could have implanted later than average. Babies grow at different rates. I was measuring 2 weeks ahead at 28 weeks. Your due date is just a guess, baby come's when he or she is ready, but I know how awful it is to go in thinking you're a whole week further along than you really are. Congrats on your pregnancy!


ETA: Based on your positive HPT, I would say you did conceive before October 16th though.

[ShawnaCAN]

Ultrasounds prior to 15 weeks can be off by up to a week, because every baby grows at it's own pace. After 15 weeks, u/s for dating can be off by as much as 2 weeks. CD17 looks like the date of conception day to me. Because the u/s is only off by about a week, just take it with a grain of salt and stick with your original due date based on the date of conception. When you're charting as consistently as you were, the date of conception is the more reliable way to calculate the due date - even more reliable than the u/s actually!

[KatiInCT]

Ultrasounds prior to 15 weeks can be off by up to a week, because every baby grows at it's own pace. After 15 weeks, u/s for dating can be off by as much as 2 weeks. CD17 looks like the date of conception day to me. Because the u/s is only off by about a week, just take it with a grain of salt and stick with your original due date based on the date of conception. When you're charting as consistently as you were, the date of conception is the more reliable way to calculate the due date - even more reliable than the u/s actually![/b]

Thanks Shawna! Is good to know even u/s's aren't perfect science.

(Although I will admit that DH loved the idea that he had "super sperm" who could live 6 days "in the trenches" as he put it.)

[ShawnaCAN]

(Although I will admit that DH loved the idea that he had "super sperm" who could live 6 days "in the trenches" as he put it.)[/b]

If that really happened, you would have only been 7DPO when you got your BFP. There's no way in heck you would have gotten your BFP at 7DPO. So you've got 4 areas of evidence that support conception around CD17 - CM, temps, the timing of intercourse, and the BFP at 14DP0. You've got one area of evidence supporting conception at another time (the u/s), but it's not backed up by anything else - not CM, not temps, not the timing of intercourse, and the timing of your BFP makes it a near impossibility!

lol @ your DH, how sweet!

[sjkduke]

At the office I worked at, all DD are based on age/size of the fetus. If baby is measuring 7 weeks/0 days, and based on your LMP you're 6weeks/0days, they base it on the u/s. That date can change along the way, too.

Good luck!

[AmandaEliz]

My OB told me that it's REALLY difficult to measure at 6-7 weeks because the baby is so tiny. Based on my LMP, my son was due Sept 24th, our 20wk ultrasound said Sept 17th & Ethan wasn't born until Sept 30th! Honestly, we obsess about it, but once you get the BFP the EDD kinda becomes irrelevant.

[kruff79]

Try not to worry about the "Due Date" too much. With my son we went from Dec 2 to Dec 23 for a due date based on u/s and he graced us with his presence "6" weeks early at 7 lbs even and 22 1/2 inches long. I am inclined to think the earlier date was more correct. Your baby will join your family when he or she is ready, with little or no regard to your timing.

[KatiInCT]

Thank you all for your replies. For my own personal counting purposes I am going to keep the earlier due date. The doctor is free to think what he wants. I know that our little one will join the world when the time is right no matter what the "due date" says on paper.

[MamaAnna]

That's a great way to look at it. With my DD they kept bouncing the due date around from mid-May to mid-June and she ultimately ended up being born on the first due date before they even did an u/s. You could hear so many due dates it'll make your head spin.