- Izabel Looney
- Aug 28
- 4 min read
What is a due date, how is it calculated and how does it affect my doula care?
When you're pregnant, your due date can feel like a magical count down to when you're finally able to hold baby in your arms but what goes into determining that date? Due dates generally are based off of the last menstrual period and assume that the expecting parent's cycles are regular, 28 days long, and that you ovulated on the 14th day, this is called Naegele's Rule. With this method they would count 7 days from the first day of your last period and then add 9 months or if you know the date of conception, like with IVF families, subtracting those 7 days and adding 9 months.
So how accurate are due dates calculated with Naegele's Rule? This rule was created in the late 1700's before there were better ways of estimating due dates and gestational ages. In the centuries, since then we have learned more about women's bodies and cycles and now know that many people experience longer or shorter cycles, irregular ovulation, and some don't know the first day of their last cycle... who hasn't lost track of cycle dates due to the chaos of life, right? Most often your provider will suggest an ultrasound to verify gestational age as research has found that ultrasound measurements in early pregnancy is a much more accurate method compared to Naegele's Rule. This said, while ultrasounds are more accurate... babies come when they want to come and it's an estimated due date for a reason. A study of 1,514 pregnant women found that if it was the woman's first time giving birth, 50% would delivery by 40 weeks 5 days and 75% would delivery by 41 weeks 2 days. They found that if it was not her first birth those numbers shifted to 50% by 40 weeks 3 days and 75% by 41 weeks. Feel free to use this information the next time you're betting on a friend or family member's baby being born. A different study that followed families before conception found only 25% of women would deliver by 39 weeks and 5 days.
Now that we know how reliable due dates are, let's talk about how this could affect doula care. Generally, most doulas I have met go on call at 38 weeks. This gives us a good buffer for most clients and we plan our on-call window for a client around a month long to account for some babies being a little early and some being a little past due. This rough plan helps us decide how many clients we can comfortably take on at one time, secure backup doulas and childcare if we have children, and help us ensure we are able to fully show up for each birth as the best doula we can be avoiding burnout. Even though we tend to officially go on-call at 38 weeks, you aren't alone if circumstances require us to go on-call early. Good communication allows us to adjust plans to better suit your family in instances where baby or babies may join us preterm like for multiples or certain medical conditions. It is so important to keep open and clear communication with your doula if anything starts to indicate baby might possibly come early so we can be ready and waiting for in case you need us. Babies truly do come whenever they want to at times and other times baby gets evicted early and keeping your doula in the loop makes a world of difference.
Beyond your on-call window, your due date helps many doulas schedule your prenatal appointments to align better with the prenatal care you are receiving from your midwife or OB. While you have access to ask us questions anywhere along your journey, aligning our prenatals with milestones in your care schedule allow us time to tackle questions that got missed by your provider, explain upcoming tests, create birth wishes you can go over with your provider at your next appointment, and support all the big emotions that can come up after appointments. One of a doula's main roles is providing informational support so you can give informed consent and have those meaningful conversations with everyone on your care team for the topics that matter most to you.
At Birch Tree Birth Services, knowing your due date, induction date, or cesarean date allows me to prioritize you and your family's care as you grow close to that magical date. I take on up to four clients a month to make sure you get the best version of me possible. Throughout your pregnancy I will see you up to three times: once at 30 weeks for everyone with a two hours going over birth wishes prenatal exploring a lot of information, once at 35 weeks for full package clients for a two hour comfort measures and postpartum planing prenatal, and lastly at 37 weeks for those choosing to add T.E.N.S. (Transcutaneous Electrical Nerve Stimulation) services. I generally go on call at 38 weeks but for families expecting multiples, with early induction dates, or a history of early babies, etc., I adjust accordingly to best fit the individual situations needs. This can look like just moving the on-call window up or it can mean adjusting the prenatal schedule to make sure they have ample time to cover all the information.
Interested in seeing if your due date is available? Schedule a free consultation below!
Sources
Baskett, T. F. & Nagele, F. (2000). “Naegele’s rule: a reappraisal.” BJOG 107(11): 1433-1435.
Morken, N., Klungsøyr, K., & Skjaerven, R.. (2014). “Perinatal mortality by gestational week and size at birth in singleton pregnancies at and beyond term: A nationwide population based cohort study.” BMC Pregnancy Childbirth 14: 172.
Whitworth, M., Bricker, L., & Mullan, C. (2015). “Ultrasound for fetal assessment in early pregnancy.” Cochrane Database Syst Rev (7): CD007058.
Jukic, A. M., Baird, D. D., Weinberg, C. R., et al. (2013). “Length of human pregnancy and contributors to its natural variation.” Hum Reprod 28(10): 2848-285.
Smith, G. C. (2001). “Use of time to event analysis to estimate the normal duration of human pregnancy.” Hum Reprod 16(7): 1497-1500.
