Traditionally, estimated due dates are calculated by taking the start date of a womans last menstrual period and adding a year, subtracting three months and adding seven days, a method known as Naegeles rule. If youre a woman whose period is like clockwork, its pretty accurate, Dr.

How does scan determine due date?

A dating scan is the most accurate way to predict your due date, also known as your estimated date of delivery (EDD). The point of the scan is to work out how many weeks pregnant you are. You may have calculated the length of your pregnancy from the first day of your last menstrual period (LMP).

Can scan be wrong about due date?

As pregnancy progresses, the accuracy of an ultrasound for predicting due dates decreases. Between 18 and 28 weeks of gestation, the margin of error increases to plus or minus two weeks. After 28 weeks, the ultrasound may be off by three weeks or more in predicting a due date.

How do you know your body is getting ready for labor?

There are several signs that labour might be starting, including: contractions or tightenings. a show, when the plug of mucus from your cervix (entrance to your womb, or uterus) comes away. backache.