What is more accurate? Date of conception or dating ultrasound?

[seenabeena]

Hi all

So I am pregnant again and over the moon, but it came as a bit of a surprise so I am not sure of when my LMP was. Since we already have 2 little sprockets our alone time is few and far between so I know the exact date of conception, however the date's of conception do not equal the date's of the dating ultrasound. Basically it's only a couple of days' difference, but when you have a history of babies that come 2 week's early and still weigh over 10lb a few day's of extra growing is a BIG difference!!!

If I go by the ultrasound date's I am only 8 week's today, but by my conception date's I am 9 week's on Sat. What are the chances of the dating scan being wrong? I know it's only a few days, but I want to know for sure.

thanks for reading my long question

[~mamaspice~]

I'd go by the date you are sure you conceived. My dating scan put me behind by about 6 days which I knew was impossible as we only DTD once that whole cycle and i got a feint positive very early. if I conceived when the dating scan said I did I would have got a positive HPT at like 5 or 6 DPO which would have been extremely unlikely. My GP swore the early dating scan was correct, but I knew better. And sure enough when I had my 12 week scan bub was measuring as per "My" dates.
Go with your gut feeling for sure

[LimeSlice]

It can take up to 24 hours for 'conception' to occur from memory, it isn't an instant thing So if it is only a day or so out, then I would think they are actually the same, iykwim.

Take the middle ground but either way, it isn't much difference.

[Mad Scientist]

Both my ultrasounds were out by 10-12 days (saying i was due later than i thought with my dates). DD1 came a month before my date and six weeks before my u/s date but she definitely wasn't six weeks early. Dd2 came right on MY due date, 10 days before my u/s due date. I'd be putting faith in your due date seeing as you were so sure of conception

[BellyBelly]

Your own menstrual cycle, always. Machines are based on averages and mathematics. We all have unique cycles hence why we never give birth on the guess date either.

[Faithful Mumma]

Yep, I would go with your conception date. I totally understand where you are coming from though....my DS was 11lbs 2 oz, although he was two weeks late (going by my conception dates).

[~Kim~]

DTD date isn't always the same as O date though. Do you know when you O'ed cos that could be the 5 days difference IYKWIM?

[Twin Sister]

I would say U/S due date since ovulation day and BD day are not necessarily the same. When I was PG with DS my LMP due date was 6 days before my U/S due date and he was born on his U/S due date.