Question by  Gilda (113)

Can you trust the dating provided to you from an ultrasound or should you depend on tracking back to the onset of your last menstural period to determine your due date?

I have two different due dates, one based on an ultrasound and one based on my LMP, which one is more accurate?


Answer by  occfiregirl (127)

I would trust the date from your last ultrasound. Your due date can vary though and even though these are off, they should not be off by much. The further you progress in your pregnancy, your due date can change again. If you are concerned, you could verify with your doctor.


Answer by  Roland27 (16334)

The LMP is more accurate than going back to the date of your last period. The Ultrasound technician takes the photos of your child and he measures the dimensions of the baby. By the size of the baby he can tell the age of the fetus and will determine your due date.


Answer by  Dana46 (2345)

The ultrasound depends on average fetal sizes to determine how old your fetus is and when the due date will be. Your LMP may be more accurate.


Answer by  tatataterri (203)

Ultrasounds are very often off. All babies grow at their own rate. You should use the date of the onset of your last menstrual period to determine the due date. Ultrasounds should be used when you don't know that date.


Answer by  alrac (197)

Accuracy of ultrasound dating decreases as gestational age increases. In the first weeks of a pregnancy, the fetus follows a very standard growth pattern so the size of the fetus directly corresponds with the gestational age. If the ultrasound was done after the first trimester, the accuracy will be lower.

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