When you're expecting a baby, it can sometimes feel like it's impossible to wait all the way until your due date to meet your little one. And when you're taking birthing classes and learning about labor, the day your baby will arrive is never far from your thoughts. But how accurate is the doctor's estimation of your impending arrival's first birthday?
As it turns out, due dates are pretty accurate. Sure, your doc may not get the exact date and time, but he or she can almost certainly pinpoint the day you'll deliver within about a week.
Due dates are calculated using something called Nagele's Rule, a simple equation based on the date of your last menstrual period. Essentially, your due date is the date of your last menstrual period plus 15 days and minus three months. For example, if you last menstrual period was on August 1, your due date would be May 15.
So while your baby may not arrive exactly on the day the doctors predict, Nagele's Rule will give you an idea of when you'll need to start packing a bag for the hospital – which is pretty useful indeed.