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Neither Myriad Genetics, Inc., nor its employees, nor any contributor to this website, makes any representations, express or implied, with respect to the information provided herein or to its use.SneakPeek aims to provide the most accurate and up-to-date information to help our readers make informed decisions regarding their health before, during, and after pregnancy. This article was written based upon trusted scientific research studies and/or articles. Credible information sources for this article are cited and hyperlinked. Due date changes in pregnancy: what to expect and why they happen If pregnancy is a journey (and it is!), then your estimated due date (EDD) is the destination. From scheduling appointments with your OBGYN and learning how do doctors calculate due date or using an online pregnancy due date calculator, to ensuring your little one is growing on track, virtually every element of prenatal care revolves around your predicted due date. Navigating these milestones can also reveal exciting details about your pregnancy, such as the chances of having a boy or girl. So, what happens when that destination shifts a little to the right or left? More than ¼ of women see a change in estimated due date during pregnancy. If your estimated date shifts within 14 days before or after your original EDD, it’s largely considered normal. These changes are even more likely towards the end of your journey—but if they happen earlier, it could indicate something important about the health of your pregnancy and future baby (or babies). Below, we break down why due date changes happen, and what you can learn from them when they do. Due Date Changes in Pregnancy: What to Expect and Why They Happen If pregnancy is a journey (and it is!), then your estimated due date (EDD) is the destination. From scheduling appointments with your OBGYN and learning how do doctors calculate due date or using an online pregnancy due date calculator, to ensuring your little one is growing on track, virtually every element of prenatal care revolves around your predicted due date. Navigating these milestones can also reveal exciting details about your pregnancy, such as the chances of having a boy or girl. So, what happens when that destination shifts a little to the right or left? More than ¼ of women see a change in estimated due date during pregnancy. If your estimated date shifts within 14 days before or after your original EDD, it’s largely considered normal. These changes are even more likely towards the end of your journey—but if they happen earlier, it could indicate something important about the health of your pregnancy and future baby (or babies). Below, we break down why due date changes happen, and what you can learn from them when they do. Estimated Due Dates 101 Setting an EDD and your baby’s gestational age is one of the main purposes of your first-trimester ultrasound. This is done by measuring your baby’s CRL, or crown-rump length, which can show with fair accuracy how long a baby has been growing in utero. In a normal, healthy pregnancy, EDD is usually cemented during your second ultrasound. The second ultrasound includes a fetal anatomy scan that measures other parts of your baby’s body to ensure it’s developing at a normal rate. However, a change in due date may be suggested if your ultrasonographer detects a discrepancy between the provided date of your last menstrual period (LMP) and your baby’s growth rate. What is Naegle’s Rule? Many providers use a principle known as Naegele’s Rule to calculate the estimated due date. Naegle’s rule hinges on two assumptions: A woman’s pregnancy should last approximately 280 days (40 weeks) A woman’s pregnancy should be dated from a woman’s last period Franz Karl Naegele was an obstetrician who died in 1851, and his rule has been used for well over 150 years. Physicians who use it apply a simple formula to arrive at an EDD: Pinpoint the first day of your last period Count three months from that date Add 1 year and 7 days to that date Naturally, the rule doesn’t account for the many anomalies introduced by the realities of women and their reproductive health. From irregular cycle lengths to simply not remembering the start date of your last menstrual cycle, exclusively relying on Naegle’s rule can’t reliably predict a baby’s due date. Imaging technology like ultrasounds—which should be administered at least twice during a pregnancy—help to account for this and clarify an estimated date. Other than an ultrasound measurement, some providers also use other methods to arrive at an estimate, like measuring the size of your uterus or using another calculation known as Parikh’s formula. 5 Reasons Why Your OBGYN Could Change Your Due Date In most cases, the ACOG discourages changes to EDD. They elaborate that changes “should be reserved for rare circumstances” and “documented clearly in the medical record,” as they can significantly alter prenatal care plans. One of the main reasons why your EDD might change is simply a lapse in reliable memory. According to research, only around 50% of women can successfully remember the date of their last period. Apart from a misrecollection of that important data point, your due date could be subject to change for any of the following 5 reasons. #1 You’re Pregnant with Twins One of the most common occasions an EDD might change is when your healthcare provider discovers you’re pregnant with twins or multiples. Carrying more than one baby can make pregnancy—and delivery—more complex because of: Different rates of development – It’s common for babies who share a uterus to develop at different rates after the 26th week. In fact, identical twins who share a placenta are at a high risk of a condition called selective IUGR, wherein one twin grows steadily while the other doesn’t grow as well. Third-trimester delays – Most twin and multiple pregnancies stall in the third trimester, around the 26-week mark, when the tight space compared to fetal size tends to restrict growth. Though this can create a much more sensitive delivery process, it’s largely considered normal in the world of obstetrics. Increased importance of EDD accuracy – The more babies are added to a pregnancy, the more important it becomes to closely observe fetal and maternal health. Miscalculations in EDD as well as other important vitals, may misguide medical decisions if you or your little ones need more care. The majority of twin or multiple pregnancies arrive earlier than singletons, which must arrive before 39 weeks to be considered premature. In contrast, many twin pregnancies result in premature births. Birth at 37 weeks is considered healthy for twins, as babies usually have sufficient lung capacity to breathe on their own. If you’re carrying multiples, it’s recommended you be prepared for labor by at least 28 weeks into your pregnancy (and be mentally prepared for your EDD to switch). #2 Your Pregnancy History If you’ve been pregnant before, your OBGYN will take your pregnancy history to look for trends that might impact your current one. Mothers who’ve delivered late or early in previous births are more likely to repeat that pattern. If you have a history of preterm or post-term birth, your care provider may recommend more thorough or frequent prenatal screenings to more accurately predict your baby’s due date. #3 You Get an Infection Getting sick during pregnancy could delay your baby’s predicted due date. Some types of infections are very common during pregnancy, including: Urinary tract infections (UTIs) – UTIs and recurrent UTIs are common in pregnancy. Even still, it’s important to treat them early with antibiotics. Untreated infections can worsen and cause major disruptions to prenatal care, putting you and your baby at risk of preterm birth or even miscarriage. Bacterial vaginosis (BV) – An estimated 25% of expecting moms develop BV while they’re pregnant. BV is the overgrowth of a naturally-occurring bacteria in the vaginal ecosystem. Though BV is common, it can augment your risk of preterm birth and raise your baby’s likelihood of having a low birth weight. #4 You Have Structural Reproductive Abnormalities If your provider finds an anomaly in your reproductive anatomy, it can impact your baby’s rate of development. Some conditions that commonly impact EDD include: Uterine fibroids – Uterine fibroids are a common type of benign tumor estimated to impact between 20 and 80% of reproductive-aged women. During pregnancy, they can raise the risk of complications like: Preterm birth Cesarean birth Breech position of the fetus Uterine fibroids can also cause pain, which raises the risk of uterine contractions that could interfere with your original EDD. Cervical insufficiency – Cervical insufficiency, sometimes called incompetent cervix, is a clinical term for having an especially weak cervix. Women with this condition are at risk of having their cervix open too early, heightening the chances that a baby will arrive before their original EDD. #5 You Use Recreational Substances During Pregnancy It’s universally accepted that using recreational drugs—whether smoking tobacco, drinking alcohol, or other substances—is harmful to fetal and maternal health. However, some expecting moms still use them, particularly if they struggle with dependency or addiction. The CDC reports the following recreational substances can directly jeopardize pregnancy timing, as well as fetal and maternal health: Tobacco Opioids Though marijuana is not directly associated with preterm birth, women who use it are considered at higher risk of untimely delivery. Similarly, alcohol does not cause preterm or spontaneous birth, but it is connected to significant developmental disruptions known as fetal alcohol spectrum disorders (FASDs). How to Reduce Your Risk of Due Date Changes During Pregnancy If your OBGYN requests an EDD change, you’ll want to work closely with them to refine your prenatal care and birth plans to match your new date. But, even before a due date change happens, there are some habits you can put into practice to reduce your risk of a schedule change: Decide on a concrete prenatal care schedule – Be sure to stick to your prenatal care appointments. If the date of your last period could be incorrect, consider adding more appointments (especially if your provider recommends it). Level up your well-being – Maternal health and fetal health are one in the same during pregnancy. From quitting cocktails to boosting your intake of critical nutrients like folic acid, one of the best ways to support your baby is to support you. Stay informed about your pregnancy – Try keeping in close communication with your healthcare provider throughout your pregnancy, particularly if you have a significant health history or a pattern of early or late births. It can feel disconcerting to deal with a due date change—particularly if you’re carrying a high-risk pregnancy, like twins—but the more conscious you can be about your pregnancy moving forward, the better. Prepare for Your Prenatal Journey with SneakPeek Every pregnancy has its share of hiccups, and looking ahead to your life as a parent can help you navigate any twists and turns along the way. Even if you’re just beginning your journey, you can learn your future baby’s gender with SneakPeek. Did you know that you can take a DNA test while pregnant? The SneakPeek Test reveals your little one’s gender as early as 6 weeks into your journey, with over 99% clinically proven accuracy and DNA-based results. You’ll take your gender blood test at home, mail it to SneakPeek labs, and we’ll triple-review your results and return them on the same day they’re received. We’ll even include a complimentary downloadable report you can share with your provider to review. Join the more than 1 million moms starting parenthood confidently by visiting SneakPeek today. Editorial Policy At SneakPeek, our commitment is to provide accurate, up-to-date, and reliable information to empower our readers. Our content is thoroughly researched, reviewed by medical experts, and fact-checked to ensure its credibility. We prioritize the well-being and education of our readers, and our editorial policy adheres to the highest standards of integrity and accuracy in all our articles. Published on January 25th, 2024 Internally Reviewed by Haley Milot, Associate Director. To ensure the highest standards of factual accuracy and reliability, all SneakPeek blog content is meticulously reviewed by our experienced internal team. Check out SneakPeek Gender Test to find out your baby's gender as early as 6 weeks with over 99% accuracy! Shop Our Products SneakPeek Gender Snap Learn if you’re having a boy or girl with the #1 OBGYN-recommended at-home baby gender test, over 99% accurate1 at 6 weeks into pregnancy. Get next-day results! Shop Now SneakPeek Fetal Doppler An easy, portable way to hear your baby’s heartbeat in between doctor visits, starting at 16 weeks into pregnancy. Shop Now SneakPeek in Local Stores Skip the wait for shipping and pick up SneakPeek Snap at select Walmart, CVS, and Walgreens stores. Just look for the kit in the pregnancy aisle, and take your test today! See Locations Sources: Verywell Family. When Your Doctor Changes Your Pregnancy Due Date. https://www.verywellfamily.com/questions-to-ask-about-changing-your-due-date-2758648 Cleveland Clinic. Ultrasound in Pregnancy. https://my.clevelandclinic.org/health/diagnostics/9704-ultrasound-in-pregnancy The American College of Obstetricians and Gynecologists. Methods for Estimating the Due Date. https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2017/05/methods-for-estimating-the-due-date National Library of Medicine. Pregnancy Dating. https://www.ncbi.nlm.nih.gov/books/NBK442018/ Johns Hopkins Medicine. Calculating a Due Date. https://www.hopkinsmedicine.org/health/wellness-and-prevention/calculating-a-due-date National Library of Medicine. Estimated Date of Delivery. https://www.ncbi.nlm.nih.gov/books/NBK536986/ Parents. Pregnancy Ultrasounds Week by Week. https://www.parents.com/pregnancy/stages/ultrasound/ultrasound-a-trimester-by-trimester-guide/#toc-why-do-people-get-pregnancy-ultrasounds Cleveland Clinic. Expecting Twins or Triplets. https://my.clevelandclinic.org/health/articles/9710-expecting-twins-or-triplets National Library of Medicine. Differences in fetal growth patterns between twins and singletons. https://pubmed.ncbi.nlm.nih.gov/30501543/ Parents. Twin Ultrasound Images From Every Trimester. https://www.parents.com/pregnancy/stages/fetal-development/twins-a-closer-look-at-your-developing-babies/ Mayo Clinic. Twin pregnancy: What twins or multiples mean for mom. https://www.mayoclinic.org/healthy-lifestyle/pregnancy-week-by-week/in-depth/twin-pregnancy/art-20048161 What to Expect. When Will Your Twin Babies Arrive? Your Tentative Timetable With Twins. https://www.whattoexpect.com/pregnancy/twins-and-multiples/giving-birth/your-tentative-timetable.aspx Verywell Family. Typical Gestation Times for a Twin Pregnancy. https://www.verywellfamily.com/are-twins-born-earlier-than-single-infants-2447481 Centers for Disease Control and Prevention. Preterm Birth. https://www.cdc.gov/reproductivehealth/maternalinfanthealth/pretermbirth.htm National Library of Medicine. Urinary Tract Infection in Pregnancy. https://www.ncbi.nlm.nih.gov/books/NBK537047/ UT Southwestern Medical Center. UTIs during pregnancy are common and treatable. https://utswmed.org/medblog/utis-during-pregnancy/ Verywell Health. Bacterial Vaginosis and Pregnancy. https://www.verywellhealth.com/bacterial-vaginosis-in-pregnancy-5272213 Healthline. How Do Fibroids Affect Pregnancy and Fertility? https://www.healthline.com/health/womens-health/fibroids-pregnancy Mayo Clinic. Incompetent cervix. https://www.mayoclinic.org/diseases-conditions/incompetent-cervix/symptoms-causes/syc-20373836 Centers for Disease Control and Prevention. Substance Abuse During Pregnancy. https://www.cdc.gov/reproductivehealth/maternalinfanthealth/substance-abuse/substance-abuse-during-pregnancy.htm The American College of Obstetricians and Gynecologists. Marijuana Use During Pregnancy and Lactation. https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2017/10/marijuana-use-during-pregnancy-and-lactation?utm_source=redirect&utm_medium=web&utm_campaign=otn National Library of Medicine. Alcohol Intake in Early Pregnancy and Spontaneous Preterm Birth: A Cohort Study. https://pubmed.ncbi.nlm.nih.gov/31803953/ Centers for Disease Control and Prevention. Alcohol Use in Pregnancy. https://www.cdc.gov/ncbddd/fasd/alcohol-use.html Related Posts January 30, 2024 Methods doctors can use to calculate due date Plenty of legends have been told about delivery day dramas, from surprise arrivals on the way to the hospital to grand entrances delayed for days. As it happens... Read More March 12, 2023 100 unique and rare gender neutral baby names Choosing a name for your child is one of the first and most significant decisions you'll make as a parent. In a world that increasingly values diversity and inc... Read More March 9, 2023 100 unique baby girl names When expecting a baby girl, you have countless important decisions to make every day. Is prenatal yoga OK for my body? Should I paint the nursery pink? Do I nee... Read More Like what you read?Subscribe to be notified on future blog posts! First NameEmail* 1 In a large-scale published study run in 2020, SneakPeek accurately determined fetal sex in over 99% of 1,029 pregnant women between 7-37 weeks gestational age. In a 2021 laboratory test, SneakPeek accurately determined fetal sex in 99.02% of 102 pregnant women using the Snap device at 8-15 weeks gestational age. In a separate published study run in 2021, fetal sex was accurately determined in 100% of 134 pregnant women at 7 weeks gestational age. In a 2022 scientific study, SneakPeek accurately determined fetal sex for 100% of 103 women at 6 weeks gestational age.
January 30, 2024 Methods doctors can use to calculate due date Plenty of legends have been told about delivery day dramas, from surprise arrivals on the way to the hospital to grand entrances delayed for days. As it happens... Read More
March 12, 2023 100 unique and rare gender neutral baby names Choosing a name for your child is one of the first and most significant decisions you'll make as a parent. In a world that increasingly values diversity and inc... Read More
March 9, 2023 100 unique baby girl names When expecting a baby girl, you have countless important decisions to make every day. Is prenatal yoga OK for my body? Should I paint the nursery pink? Do I nee... Read More