History of "Due Date"

So much mysticism and mythology surrounds the pregnancy due date. Much of the mysticism is held by physicians who hold on to the old ways of determining when a pregnant woman will deliver. Believe me, most physicians would love a way to determine the due date so we could plan our lives around the deliveries of our patients, but the truth is only 1-2% of women will actually deliver on their due date. So what determines a due date, and what is the difference between EDC (estimated date of confinement) and EDD (estimated date of delivery) and what the heck is Naegele’s Rule? This post will help show the origins of the due date and how we are currently using a system that is about 250 years old.

Franz Karl Naegele (1778-1851) was the German obstetrician who initially came up with the rule to determine a woman’s due date based on her last menstrual period (LMP). There are many ways to calculate Naegele’s Rule. I use the system where you take the LMP, add 7 days, and subtract three months. So if your LMP was April 1, 2009 then your due date would be January 8, 2010. You can impress your friends at parties with this maneuver. However, there are problems with Naegele’s Rule and many people have pointed out that this 250 year old method is no longer appropriate for our advanced age. What are some of the potential errors with calculating the EDC in this method?

Firstly, Naegele’s Rule assumes that you are having a regular period and that you ovulate on day 14 of your cycle. As a gynecologist, I can tell you that there are many women out there who have irregular cycles and may ovulate on day 20, 25, 12, 15….you get my point. This obviously would add potential error to the EDC determination and could alter the due date by days and even weeks.

There is another assumption that the routine pregnancy is 280 days based on our current calendar system. The problem with this determination is that there are many months that contain 30 days or 31 days. And what happens in a leap year, or if you are not pregnant over the shorter month of February? A movement currently exists that is trying to state that the number should be 288 days and that we are inducing women that have premature babies.

A study performed in 1990 stated that the proper method for determining a due date was to take the LMP, count back three months and add fifteen days for a primiparous (first pregnancy) woman or 10 days for a multiparous (subsequent births) woman. This was published in the journal Obstetrics and Gynecology. There are many that argue that this method of calculating the EDC is as archaic as the term EDC itself. Lending to the agrarian societies from whence it came, the EDC literally came from the fact that a woman was confined to her bed for the last part of her pregnancy to prevent preterm labor. While we still prescribe bedrest today as a possible therapy for preterm labor, it does seem odd that the medical establishment uses terminology from the 1700’s.

The due date is as individual as the pregnant mother. While the EDC is currently calculated by Naegele’s Rule, this does seem a bit archaic and inefficient; especially if we are using this dating method to determine inductions and postdatism. Other methods to determine due dates have been proposed with increased accuracy, but they require a woman to measure body temperatures and be more involved in her own self-care. Many reading this article are very involved with birth and feel as though self-care is very important, but there are many women out there that simply choose not to be observant of their own cycle.

So what do we “do” with the “due?” Today, it seems that we will keep the current system in place while continuing to back it up with ultrasounds which are accurate within 5 days if performed in the first trimester. Approximately 3% of so-called term births (occurring after 37 weeks) are completed with fetal lung immaturity and this could be because the baby may have been born between 35-37 weeks and not the completed term. Are we too involved in the birthing process? Are there better ways to determine the pregnant due date or should we not worry about the date and just let man/woman be born in his own time. The latin word natura gives rise to the word natural and means “to be born.” Maybe we should just let nature take its course.

This article was written by Shawn A. Tassone, M.D. author of “Hands Off My Belly! The Pregnant Woman’s Guide to Surviving Myths, Mothers, and Moods” – Mom’s Choice Gold Recipient and Arizona Book Publisher’s Glyph Award Winner. For more information about Dr. Tassone and his book, please visit http://www.handsoffmybellyguide.com.

Hands Off My Belly! The Pregnant Woman’s Survival Guide to Myths, Mothers, and Moods is for sale on Amazon and Barnes and Noble and at most brick and mortar stores.

Taken in whole from "History of Due Date" by Babyssentials:
http://www.babyssentials.com/first-9/basics/history-of-the-due-date-and-its-future/