The Problem With Birth E5: Due Dates
Updated: Mar 3
Hi everyone, welcome back to The Problem With Birth, I'm your host Holly Clayburn and this week I want to talk about due dates. A due date is an estimate of when your baby will be born, and is generally calculated by adding 280 days to the first day of your last menstrual period or LMP. Due dates can also be given by when conception occurred if you are certain of it, or by an early dating ultrasound that estimates the date based on measurements of your baby, both of which are more accurate than basing it off of your LMP. Your estimated due date or EDD determines how far along in your pregnancy you are, or how many weeks you are. The key word there is ESTIMATE, your due date is just a guess at when your baby will be born. The fact is though, nobody knows. These days there is so much focus on due dates, that people are forgetting that it's not a guaranteed eviction notice. Your due date can be off by as much as two weeks on either side, so don't get hung up on the exact day. Your baby knows exactly when they are ready to be born, and they don't care about our timelines. If you're ready to learn more about due dates, how they are calculated, and the actual length of pregnancy, then let's get to it.
Pregnancy is measured in weeks and days, not months like so many believe, and your due date falls at 40 weeks exactly. Your baby's development changes day by day, and week by week so this is the most accurate way to make sure that everything is going according to plan and that your pregnancy is progressing healthily. That doesn't mean that a timer dings and that your baby is automatically done growing at week 40 though. Your baby can be born anywhere between 37 and 42 weeks, and be completely normal and what's considered a term pregnancy. Let's break it down just a little bit to understand the broad definition of term.
Early term babies are born between 37 weeks 0 days and 38 weeks 6 days
Full term babies are born between 39 weeks 0 days and 40 weeks 6 days.
Late term babies are born between 41 weeks 0 days and 41 weeks 6 days
Post term babies are born at 42 weeks and 0 days or later
So you actually aren't "overdue" until after 42 weeks, even though most people say you're over due starting the day after your EDD. Like I mentioned before your due date can be off by as much as two weeks on either side because the way that it's calculated is based on the assumption that you have a textbook 28 day cycle and ovulate on day 14. We all know though that not everyone has a 28 day cycle, and that many outside factors can contribute to that. Birth control, PCOS, hormones, or just your general body can cause you to have irregular cycles, or your cycle can vary from 21-35 days and be normal. Also, even if you do have a 28 day cycle, it's not guaranteed that you ovulate on day 14. This is why I 100% recommend to everyone to track your cycle. If you're tracking your cycle then you're more likely to know when conception occurred, and then can base your EDD off of that. Due dates based on exact conception are calculated by adding 266 days to the conception date and are the most accurate calculation. However, unless you're tracking your cycle and ovulation, or used a method such as in vitro then you won't know exactly when you conceived, which is the case for majority of people.
I have said it a thousand times, I'll say it thousands more... Every body is different. It's not logical to use textbook methods across the board in pregnancy, but here we are... Still doing it literally more than 200 years after it was introduced.
The method that we use to determine your EDD based off of LMP follows Naegele's Rule. By this rule to determine your due date you add 7 days to the first day of your last period then count backwards 3 months, or forward 9. This rule is baed on the estimations of a professor from the Netherlands named Herman Boerhaave. (Honestly, I'm not completely sure I'm pronouncing that right so I'm just gonna call him professor B) In 1744 professor B studied the medical records of 100 women and based the EDD on adding the 7 days, and 9 months, except he never said if it was 7 days from the first or last day of the LMP.
In 1812, another professor named Carl Naegele added his observations on the timing of conception but he too, didn't specify if the calculations were based the first or last day of the cycle. Even though he wasn't the one who originally created this rule, he still got the credit and professor B got shafted, all because professor Gunning Bedford attributed the creation to Naegele in a text he wrote in 1872. At some point in the 1900's American texts adopted Naegele's rule and interpreted it to mean the first day of the LMP, although other texts, and OBGYN's recommended that it should be the last day. Since then, that is what all of our EDD calculations have been based on.
There have been numerous studies on the normal gestation of pregnancies in the last 30 years, and I won't bore y'all to death with all of the statistics of each of them, but in short, our current calculations are not accurate, and genetics can play a role in the length of your pregnancy, If you're a statistics person then I highly encourage you to look into these studies as I found them quite interesting. The best place I found a quick summary for them was from Evidence Based Birth.
So fun fact, only 3-5% of babies are actually born on their due dates, and typically most first pregnancies will go into 41 weeks before spontaneous labor occurs. These days though inductions right at 39 weeks are pretty standard and popular. By the end of your pregnancy there's no doubt you can't wait to meet your baby, you're probably tired, and uncomfortable but there are many benefits to waiting until your baby is ready to be born. Babies have a mind of their own, and come when they want to. It is believed that the onset of labor is caused from the fetus releasing hormones that trigger contractions to start. There is no doubt that it it this way by design so that babies are born when they are fully developed and ready. Now of course, there are instances when a baby has to be born before they are ready because of a medical reason, but in the event of a fully healthy pregnancy there is no need to induce labor. I'm not going to go into all of the ins and outs of induction or medical reasons for it on this episode, but I will do an episode covering it in the future.
Going longer in your pregnancy does come with increased risks after a certain point, but just like everything else, it is specific to you and the fetus what your risk is. Risks can include uterine or amniotic infection, low amniotic fluid, placenta abruption, c-section, forceps or vacuum assisted delivery, vaginal tearing, hemorrhaging, preeclampsia, low APGAR scores for baby, large baby, meconium, NICU stays, and stillbirth. Any of these things are possibly at any point in your pregnancy though, and the amount that these risks increase are relatively low. Again, I'm not going to dive into each specific statistic because I guarantee that your eyes will glaze over and you'll trade me in for Crime Junkie... Which btw I would totally forgive because I'm obsessed too... But I do highly highly highly encourage all of you to read up on the,. Keep in mind the relative risk vs the actual risk though, and don't take scary mommy articles at face value. There are so many things to take into consideration when you are researching all of the risks associated with any pregnancy, things like genetics, pregnancy complications, no prenatal care, smoking, advanced maternal age, and racism just to name a few. If you're wondering what in the hell racism has to do with increased risks then just stick around for a while because multiple episodes covering this topic are coming.
When you get into the final weeks of your pregnancy no doubt that the topic of induction will come up. There are numerous medical reasons to consider induction, like things I just listed, but typically as long as you are getting routine prenatal care and monitoring the well being of your baby then you can safely carry your baby until they decide they want to join you. I really don't recommend routine induction just for the sake of it, but that's another topic for another podcast. Sometimes during your third trimester your provider will change your EDD based on a more recent ultrasound but studies have proven that these are the absolute least accurate measurements of your baby, and are no cause to change your EDD unless it is the first ultrasound of that pregnancy and is more than 21 days different than the EDD based off of LMP.
If your provider doesn't bring up the topic of induction then I guarantee that your friends and family will. I can personal guarantee you 100% that your friends and family will bombard you with an onslaught of "have you had that baby yet?" texts and calls in the final weeks, and you will probably want to hulk smash your phone within 2 days of your due date. One way to combat this annoyance is to give people a due month vs a specific date, to give a season like summer or fall, or I've even known people to add two weeks onto their due date. With our 3rd pregnancy we just gave the month instead of the date and it saved me A LOT of the comments and questions! People will often say things like "oh you'll never make it that long" based on things like your size, bodily changes, or how you're carrying your baby. Reality is though, that no one can be certain WHEN you'll go into labor. Sure, your body making changes is progressing towards labor, but like we have talked about numerous times, dilation doesn't give you any indication, and things like loosing your mucus plug, loose bowls, and increased Braxton hicks don't guarantee that labor is near. Sometimes even your water rupturing doesn't kick start contractions! Your baby has to release the specific hormones to create the onset of labor.
I always giggle a little bit when I see social media posts like 6 weeks (or less) until baby X is here! While yes, it can be in that amount of time, don't expect that to be the case, especially for your first pregnancy. Some babies wait longer to be born because they simply need more time to develop, so as long as your pregnancy is low risk and healthy, I think it's best to let them pick their own birthday. Your baby can be born way before their due date, or a few weeks after, and really they are the only one who knows when it is that they are going to do that. The waiting game isn't fun, and if you're a bit of a control freak... like me... then I totally get how anxious it can make you. One thing that I can guarantee though is, you won't be pregnant forever. The last couple of weeks really feel like they take 27 years, but before you know it you'll be snuggling the sweetest little babe, and inhaling that incredible newborn smell.
Our culture is so hung up on due dates, and evicting babies right at or before that 40 week mark, and as it turns out we aren't even accurately calculating those dates. We are using an outdated, and wrongfully credited rule to determine gestation and that is The Problem With Birth.
Thanks everyone for listening to this week. I know it was a little more on the biased side of not inducing, and soon we will get to the evidence on why that's my opinion, but opinion aside, the facts surrounding due dates are in there and I hope that you take away valuable information this week. I know that not everyone has a passion for research, so any additional questions that you have, feel free to shoot me a message through the website theproblemwithbirth.com or on facebook or instagram @East Texas Birth Co
You can also suggest topics that you'd like to hear in the coming weeks, or email about doing a collab episode. I love love love doing this podcast each week and helping to educate folks so please do me a huge favor and be sure to share a link on all of your social media, with your friends, and family and to rate 5 stars and leave a review on Apple Podcasts. Like always, the transcript of this episode will be made available on the East Texas Birth Co blog so that anyone who is hearing impaired can still benefit and learn from this resource. Be sure to subscribe and tune in next week to hear me discuss even more on The Problem With Birth.