Why Your Pregnancy Isn't Likely To End On Your Due Date

You missed your period. You wonder if it's stress, or if you're finally pregnant. A few days or weeks go by, and you decide it's time to take a pregnancy test. It comes up with two lines, plus signs, plays a tune or fireworks go off.  You're pregnant!  After the shock, excitement, "WTF" moment goes by you go to the doctors. After the blood tests and everything else you have to do, they take a paper wheel out, ask you when your last period was and you get a date.  The magic date. The date goes into your calendar so when people ask when you're due, you tell them and anxiously await this date coming.

However, this date you are given is an "Estimated" Due Date. The World Health Organization (WHO) actually lists full-term pregnancy as anything from 37 weeks gestation to 42 weeks gestation. So your due date is in the middle of five weeks, which means your birth could happen anytime in that period. The calculation to determine this date- called Naegle's Rule- was created in 1830 by a German doctor named Dr. Franz Naegles. It's based on the assumption that it takes 280 days to gestate a baby. You're meant to add nine months and seven days to the first day of your last menstrual period.

But this "Rule" hasn't been updated since its original creation. Therefore, it doesn't take into account that birthing parents are older on average than they were back in the 1800s. The rule also doesn't consider that nowadays, we have much better medical care than they did two centuries ago. You could also argue better nutrition, but that one's shaky if you consider the rise of fast food and other unhealthy foods.


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Plus, the calculation was created by a German doctor that's based on his limited experience with only German birthing parents. Other ethnicities and cultures around the world can have different experiences that aren't taken into account. Because of stress, hormone influencers like genetically modified foods and hormone contraceptives, having a perfect 28-day cycle isn't as common as it used to be.

Given all these changes over the past two centuries and the vast amount of exceptions that aren't taken into account, it's no wonder that only 5 percent of birthing parents will actually go into labour on their due date. Meanwhile, approximately 50 percent will give birth past that 40-week date, usually within 7 days after. This is such a common occurrence that some countries, including France, have actually taken the due date you would get from Naegle's Rule, and are then adding seven days to create a more accurate due date.

So when your due date comes and goes, don't think that your body's broken. It's actually working perfectly. Your baby ultimately knows when they're ready to come out, and your body will keep your baby safe in the meantime (unless a medical reason comes up to warrant a medical induction). So take this time in the last weeks of pregnancy to prep for postpartum recovery, reconnect with your partner and friends, and rest. That's because when your baby comes, your life will change in ways you never thought possible.

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