When a doctor performs an ultrasound, they write a report on the findings and include two estimated due dates.
The first date is calculated using the date of the LMP, and the second date is based on the ultrasound measurements. When your doctor evaluates the ultrasound results, they’ll determine whether or not these dates are in agreement.
The other way to calculate your due date is to use a pregnancy wheel. It’s very easy to estimate your due date if you have access to a pregnancy wheel. When you line up that date with the indicator, the wheel will display your due date. Luckily, there are ways to figure out your due date when you can't remember the first day of your LMP.
If you know you had your LMP during a particular week, your doctor can estimate your due date accordingly.
Diagnostic ultrasound is a sophisticated electronic technology, which uses pulses of high frequency sound to produce an image.
This is why ultrasound measurements can’t be used to accurately predict the age of the baby in the later stages of pregnancy.Your doctor probably won’t change your due date unless its significantly different from your ultrasound date.If you have more ultrasounds, each ultrasound report will contain a new due date based on the most recent measurements.Your doctor may change your due date based on the ultrasound measurement.This is most likely to occur in the first trimester, especially if the date estimated by the ultrasound differs by more than one week from the date estimated by your doctor based on your LMP.