The Lie of the EDD

In my trusty birth resources binder, prepared for us by our Doula Lynn, I arrived on an article titled, "The Lie of the EDD: Why Your Due Date Isn't when You Think". It was an interesting read. As you may have guessed from the title the article deals with the common misconception that a full term pregnancy is a max of 40 weeks based on Naegele's Rule.

Here are a few tidbits from the article:


"There is one glaring flaw in Naegele's rule. Strictly speaking, a lunar month is actually 29.53 days, which makes 10 lunar months roughly 295 days, a full 15 days longer than the 280 days gestation we've been lead to believe is average. In fact, if left alone, 50-80% of mothers will gestate beyond 40 weeks."


"They found that for first time mothers (nulliparas) pregnancy lasted an average of 288 days (41 weeks 1 day). . . . To easily calculate this EDD formula, a nullipara would take the LMP, subrtract 3 months, then add 15 days." 


According to this calculation my EDD could be April 2, 2011 instead of March 25, 2011 . . .Yikes!!


"One of the most vital pieces of information to know when you are expecting is that ACOG itself does not recommend interfering with a normal pregnancy before 42 completed weeks."