Hello I was wondering how accurate are ultrasound in first trimester? My lmp was july 18th which would give me a due date of april 24th but when I went for an ultrasound they said my due date is april 18th.. Which one should I go with? I need to know when I conceived if someone can help me?
Like ladyboo and you, my little girl measured 2 weeks bigger than she should have been based on lmp. I was due august 19 and now I am due on august 7th. They are going by the latter date.
They told me that most babies measure uniform during the first and second trimesters. It's not until the last trimester that they start to gain differently. (not sure how true this is it's just what the ultrasound tech told me.)
Ultrasounds in the first trimester can be very inaccurate as far as being able to tell a due date.
Your best bet is to go by when you think you actually conceived-which would be sometime about a couple of weeks after your last period, most likely.
And remember, there's nothing that can really tell you exactly what day your baby is "due", it's more like an "estimated time of arrival" and it can very reasonably be off 2 weeks in either direction or even more and be just fine. Everyone has a slightly different temperature "oven", so their little biscuits are done a little different rate.
If you tend to have regular periods, and they are exactly 28 days in length, you can probably go by the due "week" the doctor tells you pretty reliably-but remember, it still might be up to 2 weeks in either direction.
If your cycles tend to be longer, expect a slightly longer pregnancy, if your cycles tend to be shorter, perhaps the baby will be a little earlier.
Mostly, just take in the fact that, no matter what technology we apply, nature's plan is to allow us the opportunity to relinquish control a bit, and to help us relax into the process-even if it's kicking and screaming all the way! It's a good exercise for motherhood!