The precise breakdown goes something like this: should a woman's LMP and the ultrasound conflict by more than 7 days and the ultrasound was performed before 14 weeks, the due date should be changed to reflect the dating by the ultrasound.
Should the ultrasound have been performed earlier than the 9th week, and the due date is off by 5 days according to LMP, the due date should be adjusted to the one indicated by ultrasound.
An early ultrasound is one performed at less than 14 weeks.
It is estimated that 40 percent of pregnancies would have a change of due date is using the ultrasound to date the pregnancy. American College of Obstetricians and Gynecologists.
To make the most accurate range for a conception or due date, the best method is to become aware of your normal cycle. References "Due Date Calculator." Calculate Due Date From Ultrasound Report.
Dating Scans A scan can date the time of conception if you are uncertain of when your baby was conceived.
The guidelines give precedence to the findings of an early ultrasound over other methods, including date of last menstrual period or LMP.
The error margins are not much greater than those scans carried out in the second trimester.
It will also help physicians to know if a fetus is growing as it should.
This new guideline was actually the first time ACOG has issued a statement on the topic of how to accurately date a pregnancy.
Up to 50% of women are uncertain of their dates, or have an irregular cycle, or have just stopped the oral contraceptive pill (OCP), or are lactating or did not have a normal last period.
Enquire when the women had her first positive pregnancy test (which may be positive 3 days before the missed period).” HSE, National Guideline The benefits of getting your conception dated is that it enables you to have some idea of when to expect your baby so that you can make plans both medical and otherwise for his or her arrival.
Before 12 weeks, your uterus is safely tucked within your pelvis.