Knowing how to calculate gestational age will help you know your due date
You are pretty sure you are pregnant. At least, the six pregnancy tests that you took said so.So when is your baby due? With your obstetrician's guidance, you will learn how to calculate gestational age.
When you go for your first medical appointment, you will be asked the date of your last menstrual period. (Note to women: You are supposed to keep track of this sort of thing.)
Let us say your last period was May 1. The doctor will count back nine months to February 1 and add a week. Your due date is February 8.
Or you can add 280 days to the first day of your last period. If your last period started on (let us make it easy) January 1, add 280 days and you will discover that you are due on October 8.
Another way is to add seven days to the last menstrual period, subtract three months and add one year. If your last period was April 10, 2011, add seven days, which makes it April 17 and now subtract three months. You are due on January 17, 2012.
Of course, the doctor actually has a wheel-like apparatus that makes it easier for her to do the gestational age calculations, as if counting back three months and aging a week is difficult even for the most mathematically challenged.