Why Your Due Date Is Also an Intervention

Your baby will arrive at the right time, regardless of your due date. Adriana Lozada explains how due dates are influenced by factors out of your control, and why you shouldn’t worry too much about them.  

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Why Your Due Date Is Also an Intervention

Adriana Lozada: Hello, mighty parents and parents to be. I’m Adriana Lozada and you’re listening to Birthful, and today, just like every other week, I’m here on my own talking one on one to you. Today, we’re gonna talk about a great pet peeve of mine, which is the concept of the due date. And when are you due is probably the first question you get asked by anybody after they know you’re pregnant, and the fact is the due date can bring a lot of comfort, like it provides you with a timeframe for planning all the things that need to happen, both relating to medical visits and tests, and also getting ready for your baby, and I’m a big fan of setting dates because inevitably they arrive and yay, your baby’s here. The problem is that so many decisions are being made based on this information, this due date, that is tenuous at best, and it is not based on current evidence, nor does it take into account variations in menstrual cycle length or population differences. 

So, first we need to take a step back and take a quick look at how due dates are calculated, which is based on something called Naegele’s rules, and the first problem with Naegele’s rule is that it assumes that you have a 28-day menstrual cycle, and that you ovulate on the 14th day. Those are big assumptions that are not the case for many people. Then the calculation follows is you take the first day of your last period and add 280 days, or 40 weeks to it, and boom, that’s your estimated due date. 

Now, ultrasound measurements provide more accuracy when determining gestational age, and the best time to have that ultrasound is early in pregnancy, around 11 to 14 weeks. But still, what the research shows is that even though this early ultrasound is the most accurate in estimating the date of birth, there is still a variation of plus or minus 11 days. That’s more than a week before or after the due date. And you might be thinking, “How about ultrasounds in the third trimester?” Those are the least accurate for dating the gestation of your child. And heads up that having your due date adjusted at that point can actually make your due date less reliable. 

Now, the assumption that a pregnancy is 40 weeks long is also misleading, even though that pregnancy app may be enticing you to believe otherwise by telling you that your baby has grown from say the size of a peach to the size of an orange this week. Your baby is growing at their unique rate and they will signal when they are ready to come out. So then, how long is pregnancy? Let’s take a look. 

According to the American College of Obstetricians and Gynecologists, ACOG, a baby is considered term anywhere between 37 and 42 weeks. Then that gets further divided into categories with early term being from 37 weeks through 38 weeks and six days, so almost 39, and then full term is from 39 weeks through 40 weeks and six days, so almost 41, and late term is from 41 weeks through to 41 and six days, so almost 42. And then post-term is after 42 weeks. So, that range of being term is really broad, from 37 to 42 weeks. That’s a five-week range, more than a month, with full term being between 39 and 41 weeks. 

Now, let’s look at when babies are actually born. First off, if you need more confirmation of how hopeless it is to try to pinpoint when birth will happen, consider that only about four to five percent of babies are born on their due date. That means that 95% are born on some other date. Then, if we look at all the available data for first-time birthing people, basing calculations on their last menstrual period, so figuring out like Naegele’s rule, we get that half of them will give birth at 40 weeks and five days, and half of them will be after that. So, the average for first-time birthing people is 40 weeks and five days. 

Then, if you look at 75% of babies, they will be birthed by 41 weeks and two days. And if you’ve birthed before, then those stats change to 40 weeks and three days for 50%, for that half, and then 41 weeks for that 75%. Meaning it’s a safe bet to rather consider your due date actually a week or so past the due date that you are given. And by now, you’re thinking, “I get it, due dates are incredibly inaccurate. My baby isn’t a library book that’s due at a certain time. And if a due date comes and goes, that’s totally normal and expected and I won’t worry about it. Got it.” But  the problem is that as the estimated date of delivery gets closer, it starts messing with your mind. It feels like a deadline. Everyone around you starts focusing on it and your provider may start scheduling you for an induction just in case, and then you might start doing all the things to try to get labor going. 

A word on risks and inductions. As we know, there is a risk to everything in life, and so here there can be risks for waiting and risks for not waiting for your baby to be born. Usually, the most common given reason for wanting to induce by 41 weeks is that there is an increase in the incidence of stillborn at that point. And that can sound incredibly scary, so let’s look at the numbers. Research from 2019 that looked at studies of 15 million pregnancies reported that the risk of stillbirth increases with gestational age. So, from 37 weeks, the risk slowly increases but remains less than one per 1,000 births up to 41 weeks. Then, at 41 weeks, there is an uptick. 

Depending on the birthing person’s risk factor, that increase at 41 weeks can go up to 1.66 out of 1000 births, which some may still consider a small absolute risk. Inductions also carry their own variety of risks, including prematurity, higher rates of cesarean birth, fetal distress, and other complications. So, it’s important to weigh all the risks for and against for your particular situation. However, my main point is that centering care around an inaccurate due date can become a ridiculous mind game that actually counters what you need to do to get labor going, which is have plenty of oxytocin flowing through your body. 

So, to lessen the stress ahead of time, you might want to give people around you a range of when to expect your baby to arrive, like say late May instead of May 20th. Another technique is to simply take whatever date you’re given and then add a week to it in your mind, so that if that initial date comes and goes, you’re not gonna care as much. Or you can also create a post-dates pampering list, and this I do with all my clients, and then you write in two weeks worth of daily pampering activities, one for each day past your due date. Make them indulgent. Something that you would really look forward to doing as the days go by, and that will help increase your oxytocin flow. Or you can repeat to yourself, “Due dates are guesstimates. Due dates are guesstimates. Due dates are guesstimates.” 

Whatever you end up doing, I hope that you have a wonderfully flowing birth and that your baby shows up at exactly the perfect time for them. You can connect with Birthful on Instagram, @BirthfulPodcast, and to learn more about Birthful and my birth and postpartum preparation classes, go to Birthful.com. 

Lozada: Birthful was created by me, Adriana Lozada, and is a production of Lantigua Williams & Co. The show’s senior producer is Paulina Velasco. Jen Chien is executive editor. Cedric Wilson is our lead producer. Kojin Tashiro mixed this episode. Thank you for listening to and sharing Birthful. Be sure to subscribe on Apple Podcasts, Amazon Music, Spotify, and everywhere you listen, and come back next week for more ways to inform your intuition. 


Lozada, Adriana, host. “Why Your Due Date Is Also an Intervention.” Birthful, Lantigua Williams & Co., March 24, 2021. Birthful.com.

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