Many patients believe that the later in pregnancy an ultrasound is performed, the more reliable the EDC calculated by the ultrasound is.
Perhaps this is because patients reason that since we can see more detail on ultrasound the further along one is (where we can see noses, ears, fingers, the chambers of the heart, etc.) the numbers should be more accurate. Just as children and adults of the same age can vary dramatically in height and weight, when a baby is past the first trimester he/she also can be larger or smaller than average, depending on genetics (how tall the parents are, how much they weighed at birth), nutrition, and coexisting medical conditions (diabetes, high blood pressure, etc.).
In fact, the only time that this doesn't apply is when the date of conception is known without doubt, as when an infertility patient conceives with timed intercourse or artificial insemination.
At around seven weeks of pregnancy, it’s reasonably common for women to have their first ultrasound.
An ultrasound can help you determine how far along you are in your pregnancy.
Before you consider abortion or seek an abortion clinic, it is important to know how many weeks pregnant you are (the gestational age).
The ideal time for a sonographer to assess the gestational age in the first trimester is between 7-10 weeks of pregnancy.
Other information used to calculate the gestational age, or the number of weeks and days from the first day of the last menstrual period (LMP), includes the size of the uterus on pelvic bimanual examination.Both these situations are considered largely avoidable.In our practice, the EDC will be determined at the first prenatal visit whenever possible, and subsequent ultrasounds, which often will report a different (often earlier) EDC will not override the first EDC.However, it is extremely common to encounter patients who have irregular or infrequent menstrual cycles, or have fibroid tumors that cause their uterus to feel enlarged on pelvic exam, or who conceive shortly after a pregnancy ends (without ever actually having had a period after the last pregnancy), or who got pregnant while taking birth control pills, and these situations often render the above methods useless and misleading when trying to figure out a reliable EDC.This is where our wonderful ultrasound machines can make a crucial difference.