Usually at your first pregnancy appointment someone, either the nurse, doc, or midwife, will pull out a little cardboard spinner. This person will ask you the date of your last menstrual period (LMP,) spin it around a bit, and declare you are due on such and such date.
Most women will remember this date, repeat it over and over to their friends, relatives, strangers, and even themselves. After thinking about this date so long she and everyone around her tend to forget that this is an Estimated Due Date (EDD) and that babies rarely come on that day.
The way we calculate due dates is based on a system created by Franz Karl Naegele in 1812. He used an unscientific method based off of observation and biblical study. Now if it was 100% inaccurate we would have ditched it by now, but the main takeaway from this post is that EDD’s are just that, an ESTIMATE, that is based off of LMP (last menstrual period,) ultrasound data, and, rarely though most accurately, date of ovulation.
The Naegle Rule, which is what that little spinner is using, is based off of your LMP. The problem with this is that it is assuming a 28 day cycle with ovulation occurring exactly halfway through at 14 days from your last period’s start day. Now, not many women have an exactly 28 day cycle and even those who have one do not necessarily ovulate exactly on day 14.
For instance, my cycles tend to be about 28 days, but after charting my cycles I learned that I ovulate early, usually on day 10. Right there puts that little wheel off by 4 days. When I got a first trimester ultrasound, the most accurate for dating, my baby measured exactly to MY date and not my LMP.
I’m at the opposite end of the norm, though, and many women tend to ovulate LATER than 14 days as opposed to earlier. The problem that comes with LMP dating in those cases is that mom will often be induced due to fears of being overdue when in reality she hasn’t hit the 40 week mark yet and baby just really isn’t ready.
*ACOG (American College of Obstetricians and Gynecologists) states that a pregnancy is not overdue, or postdates, until 42 weeks of pregnancy. *
We have also been led to believe that any pregnancy is full term 38-42 weeks when in reality you are not considered full term until 39 weeks. 38 weeks and 6 days is considered early term. While the baby may be perfectly fine it is still best to avoid delivery before 39 weeks unless there are other medical factors in place that make continuing the pregnancy more dangerous than the risks of an early term baby.
All of this has led some ob’s and midwives throughout the world to change to a due month. I think that this is a much healthier way to view your EDD. You would think about being due 2 weeks on either side of your EDD.
A due month would give mama and everyone else around them the chance to accept that baby’s and mom’s body’s do not follow the calendar as we know it. Do we question when a teen hits puberty one year earlier or later than their peers? No, in the case of most other physical milestones we don’t even question that everyone develops differently. Yet for some reason once a women gets to that magic date everyone including herself gets antsy and starts asking non stop if the baby is here. Even many care providers will start talking induction upon hitting that date even though the evidence doesn’t support it.
During your pregnancy do some research on due dates and the risks and benefits of going past 40, 41, 42 weeks so that if you do go longer you can be prepared to make decisions based upon facts and not based upon being uncomfortable, ready to be done, or pressure from well meaning friends or even your provider.
If, with the facts in hand, you do choose to induce you know the decision was made for good reason and is the healthiest option!
So I beg you, please, please don’t set your heart upon a specific date. There are many variations of normal in a woman’s cycle and many variations of normal as to when a baby is ready to come. Enjoy preparing for your ‘Due Month.’