Video:How to Figure Out Your Due Date

Transcript:How to Figure Out Your Due Date

Hello I’m Dr. Stuart James Fischbein. I’m a fellow of the American College of Obstetrics and Gynecology. My website is www.BirthingInstincts.com and I’m here today on behalf of About.com to discuss with you how to figure out your due date.

Due Date is Always Approximate

Sometimes figuring out when your pregnancy is due can be very confusing because there are so many formulas and sometimes it’s calculated by the first day of your last menstrual period and so most books on pregnancy, like my own book "Fearless Pregnancy" discuss what we call menstrual weeks or from the first day of your last menstrual period. If you look at a book on embryology however, you are looking at gestational weeks, which is always about two weeks less. And I know that doesn’t make a whole lot of sense, but it all started because we used to date pregnancies based on the first day of your last menstrual period because before the age of technology that’s all we had and women could usually remember that date. And from that date, it is approximately 280 days until what comes up to be your due date. Or it’s about 266 days from conception.

How to Calculate Your Due Date

And the easiest way to figure that out is if you have regular cycles is to take one of these obstetrical wheels, or nowadays they have them on your computer or on your cell phone, they have apps to tell you how to figure that out, you just put in your last menstrual period and it’s going to come out with a due date. And it just gives you a due date that helps to define when your baby is supposedly about ready to come.

Another way to figure out your due date is also to take the first day of your last menstrual period, subtract 3 months, and add 7 days. And that gives you about the same estimated date of confinement which is what a due date is, or your doctor may call it an EDC. That gives you the same one as the wheel or what your app will do. But let’s talk about due dates for a second because it’s important that we understand how vague they really are. Conception doesn’t necessarily occur the day you had sex. It can occur several days later as sperm can live for 3 or 4 days in the vaginal environment.

Normal Due Dates Occur in a Range

So it’s important not to place too much emphasis on your due date. You’re going to need it for documentation, you’re going to need it for forms to fill out, insurance, disability, your prenatal record. But just remember that anywhere from about 3 weeks prior to that due date until about 2 weeks after that due date is considered normal. A lot of times if you go three weeks before they are worried that your baby is going to be coming early and if you go more than a few days after your due date they’re calling you post-dates. That’s not accurate. You’re not post-term pregnancy until you’re beyond 42 weeks. Now, your doctor may want to begin testing after 40 weeks and that’s something that you can discuss with him, that may be something that he or she chooses to do in the pregnancy but don’t fall into the trap that you’re overdue.

And remember that a lot of your family members and friends are going to write down your due date and they are going to be calling you the day or two after your due date wondering what’s happening, why haven’t you delivered yet? What is your doctor doing? Do not let the due date disturb you. Only about 8% of women actually deliver on their due date, so you have something that’s about 92% inaccurate.

Again, I’m Dr. Stuart James Fischbein. Thank you so much for watching. If you would like to learn more, visit us online at About.com.