The details are rather technical, but the length of a normal pregnancy is anywhere from 37-42 weeks. The widespread belief that every pregnancy has to be 40 weeks is a fallacy that leads to many babies being delivered before they are fully ready.
My first pregnancy went 2 weeks past my given due date, and I was induced. Had I actually been better informed at the time on many various topics, I’d probably have done it differently. With baby number 2, I went into natural labor at one week “post-date,” and with baby number 3, I was actually 2 weeks and a couple days “overdue” according to my doctor’s estimated due date (much to the consternation of the midwife on duty at the hospital!). But all three pregnancies were, thankfully, healthy and uneventful.
These experiences have led me to conclude that my babies are just not ready to come out by 40 weeks. And what’s wrong with that? The Lie of the EDD: Why Your Due Date Isn’t when You Think says that “if left alone, 50-80% of mothers will gestate beyond 40 weeks.” Misha Safranski goes on to explain that the 40 week due date is based upon Naegele’s Rule. This theory was originatedin 1744, and is based upon evidence in the Bible that human gestation lasts approximately 10 lunar months. The formula was publicized around 1812 by German obstetrician Franz Naegele and since has become the accepted norm for calculating the due date. However, strictly speaking, a lunar month (from new moon to new moon) 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.
A More Accurate Calculation
The best way to determine an accurate due date, no matter what method you use, is to chart your cycles so that you know what day you ovulate. An alternate way to calculate your due date would be like this: For a first-time mother, take the date of your last menstrual period, subtract 3 months, then add 15 days. For women who have previously given birth, take your last menstrual period, subtract 3 months and add 10 days.
Avoiding Unnecessary Induction
The induction of labor, while occasionally prudent, has reached epidemic proportions over the past two decades. If you come under pressure from a care provider to deliver at a certain point, you can be armed with the knowledge that the American Congress of Obstetricians and Gynecologists itself does not recommend interfering with a normal pregnancy before 42 completed weeks. Knowing your true conception date and EDD (estimated delivery date) can help you and your baby avoid much unnecessary trauma throughout the labor and delivery. Remember, babies come on their own time, and sometimes all it takes is a bit of patience in waiting for him or her be born when s/he is truly ready.
There are some risks associated with post term pregnancies. Tests and careful monitoring during the last weeks of pregnancy can help reduce the risks of anything going wrong for you or your baby.