What is the most accurate way to calculate your due date?

The most common way to calculate your due date is to start with the first day of your last menstrual period (LMP). Add 7 days, and then count backward 3 months. For example, if your last period started on March 20, you would add 7 days to get March 27. Then subtract 3 months to get a due date of December 27.

Is calculating due date by conception accurate?

No estimated due date is ever 100% accurate, and even ultrasound scans aren’t entirely accurate. However, the ACOG notes that the most accurate method of confirming gestational age is an ultrasound measurement of the fetus or embryo in the first trimester, citing an accuracy of +5-7 days.

How much due date is accurate?

More than 90% are born two weeks either side of the predicted date. But, as noted above, only 4% (or 4.4%, ignoring pregnancies with complications etc) are born on the predicted date itself – in other words, the chance of this happening is less than one in 20.

Can the ultrasound 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.

Can scan due date wrong?

Can LMP be wrong?

SYNOPSIS: Clinical determination of EDD, 280 days after the last menstrual period (LMP) still plays a role but may not always be accurate due to variability in length of an individual woman’s cycle length or timing of ovulation.

How can I guess when my baby will be born?

To determine a due date, doctors use a simple calculation using the first day of a woman’s last menstrual period. They then add 280 days to get to what would be considered a “term” baby: 40 weeks of gestation. “This can be confirmed, ideally, by a first trimester ultrasound,” Fogle said.