Ultrasound accuracy dating conceive
Ultrasound uses the size of the fetus to determine the gestational age (the time elapsed since the the first day of the last menstrual period).
The accuracy of the ultrasound estimate of the gestational age varies according to the gestational age.
There are multiple methods used to determine a baby's gender, some more reliable than others.
Using fetal heart rate as a way to determine a baby's gender is based in myth, despite being believed to work for many years.
Babies with abnormalities tend to accumulate more fluid at the back of their neck during the first trimester, causing this clear space to be larger than average. The NT scan must be done when you're between 11 and 14 weeks pregnant, because this is when the base of your baby's neck is still transparent.
The scan will usually show that your pregnancy is less far along than suggested by your LMP. This means that accurate dating reduces your chance of having your labour induced because your baby is thought to be overdue.