How Accurate Is The Due Date
The pregnancy calculator gives you an approximate due date, which it works out your due date by adding 280 days to the first day of your last menstrual period . Your period and ovulation are counted as the first two weeks of pregnancy. If you have the baby on your due date, your baby has been growing for 38 weeks, not 40, but you are still classed as 40 weeks pregnant.
Factors Affecting Due Date
With so much focus and excitement over an assigned day, youd think itd be an accurate numberbut its not always the case. The simple truth is that only 5 out of 100 women will deliver their babies on their actual due date.
Still, determining which week of pregnancy youre in is crucial to receiving good prenatal care and planning for your upcoming life change.
The majority of babies are born over a 35-day span, with birth occurring anywhere from about 37.5 weeks to 42.5 weeks. Due dates also not deadlines. You could have your baby a week later than your due date and still be considered on time.
There are many factors that can influence your due date.
- Each pregnant person has their own predetermined schedule. Many people will tell you that their pregnancies were all about the same length. If you had two kids, each delivered around 41 weeks, your third kid is likely to arrive around 41 weeks.
- People pregnant for the first time tend to go into labor later. Youre more likely to go a few days past your due date with your first baby.
- Some people are at risk of preterm labor. About one in 10 pregnancies end with premature delivery. Maternal risk factors for prematurity babies include having a previous preterm birth, vaginal bleeding during pregnancy, diabetes, high blood pressure, smoking, and even periodontal disease.
Actual Length Of Pregnancy
The actual length of pregnancy varies significantly among women. Just 4% of babies are born on their estimated due date, while 70% are born within ten days. The remaining 30% are born more than ten days before the due date or more than ten days after.
The reference above provides a delivery birth range of 38 weeks and four days to 41 weeks and three days with a probability of 70%.
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About Due Dates And Their Limitations
One of the most common questions you’ll hear when you’re pregnant is, “When are you due?” Most likely, your prenatal care provider gave you a specific day, which you circled on your calendar.
But like most questions about life and about children, the answer is usually more complicated than that.
Our language about due dates reflects our need for things to be on time. Even the baby is considered “early” or “late.” We have such a social stigma around being late, but due dates are estimations, not deadlines. But because most due dates are deadlines, we tend to project that framework onto birth. People who tell their family and friends a due date may have to endure 50 calls a day asking, “is the baby here YET?” for an extra week.
But babies are not library books–no one’s going to charge your baby an overdue fine. We’d prefer not to see babies come very early or late, but most babies come within a window of 2-3 weeks on either side of the due date–right on time.
Ultrasounds In Later Pregnancy
It is common for each ultrasound throughout pregnancy to predict a different due date. Earlier ultrasounds are more accurate in terms of predicting the due date, so that’s why doctors will usually use the dates and measurements from the first ultrasound of the pregnancy as a reference.
As pregnancy progresses, the accuracy of an ultrasound for predicting due dates decreases. Between 18 and 28 weeks of gestation, the margin of error increases to plus or minus two weeks.
After 28 weeks, the ultrasound may be off by three weeks or more in predicting a due date. Thus, later in pregnancy, ultrasound measurements are more valuable for evaluating the baby’s growth over time than they are for predicting a due date.
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How To Use The Due Date Calculator:
Few things can compare to the rush and excitement of when you take a pregnancy test and read out the positive result! Once youâve processed the news that youâre going to be a mom, your thoughts will naturally turn to planning and one of your first questions will no doubt be: when is my due date? Use these three simple steps to find out how far along you are in your pregnancy:
Keep in mind every pregnancy is unique and the result will be an estimation rather than a fixed date.
First Day Of Last Period
Most pregnancies last around 40 weeks , so typically the best way to estimate your due date is to count 40 weeks, or 280 days, from the first day of your last menstrual period .
Another way to do it is to subtract three months from the first day of your last period and add seven days. So if your last period started on April 11, you’d count back three months to January 11 and then add seven days, which means your due date would be January 18.
This is how your doctor will estimate your due date and its a pretty solid target. But remember: Its just as normal to deliver a week or two before or after.
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When Are You Most Fertile
Our calculator can help you discover the most fertile days of your menstrual cycle or your Estimated Fertility Window based on the information you provide. Inexpensive, early detection pregnancy tests and ovulation test kits can be purchased online from our corporate sponsor Fairhaven Health.
Find out a date for your next period and when you could possibly receive a positive pregnancy test .
Since it is so difficult to pin down exactly which day a woman ovulates, we give you a 10-day window of when ovulation is most likely to occur.
If you are trying to conceive, APA suggests having intercourse every other day in this window. If you are trying to prevent pregnancy, avoid sex within this window and the 3-5 days before, or at least ensure you are using a condom consistently and correctly.
Pregnancy Calculator: How Is Your Due Date Calculated
While itâs true that most pregnancies last 40 weeks, there are other factors at play which will determine your due date. Most expectant mothers donât realize that both menstrual and ovulation periods count as the first two weeks of pregnancy. Many wonât be aware of their pregnancy until their first missed period, and by that time they could be up to five weeks in. That means that simply estimating nine months from the day you take a pregnancy test isnât going to calculate your due date, and, even so, factoring in a few weeks here and there for ovulation wonât either.
Unless you can pinpoint exactly what point of your ovulation cycle you were in at the time of fertilization, itâs difficult to know how far along you are and what date youâll meet your baby. Luckily, our due date calculator can help.
Using both the date of your last period and the length of your regular cycle, or exact date of conception, our due date calculator will quickly work out your estimated due date, tailoring it accordingly for longer, shorter, and average cycle lengths.
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Problems With Formula Methods For Calculating Edds
Despite the popularity of LMP formulas, they have a number of drawbacks.
Not all women ovulate on day 14 of their cycles.A major problem with formula methods is the assumption that all women ovulate on day 14 of their cycles. This can result in the fetus appearing to be several days younger or older than it really is. Research shows that not all women ovulate on day 14, even those with regular 14 day cycles.
Irregular Cycles
What If I Dont Know The Date Of My Last Menstrual Period
This is more common than youd think. Luckily, there are ways to figure out your due date when you cant remember the first day of your LMP:
- If you know you had your LMP during a particular week, your doctor can estimate your due date accordingly.
- If you have no idea when your last period was, your doctor may order an ultrasound to determine your due date.
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What Exactly Is The Date Of Conception
The date of conception is the day that the egg and sperm meet.
Women who track their ovulation may know their exact date of conception. But for many women, date of conception can be tricky to pinpoint.
Sperm can live in a womans body for up to five days, and the ovum can live for up to 24 hours after being released. In other words, you have a six-day window where you could potentially get pregnant each month.
Do you already know your due date but want to know when you likely conceived? Try our reverse due date calculator.
How Long Do You Ovulate
For women who have a 28 to 32-day menstrual cycles, ovulation can take place between days 11 through 21, but it will only occur on ONE of these days. Remember, this is just an average of days that ovulation could take placeevery womans cycle is different.
Ovulation itself only lasts for 12-24 hours that is how long an egg is available for fertilization.
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Disclaimer About The Calculator
Our calculator strives for the highest accuracy, but your pregnancy progress may differ from the calculator’s results for several reasons including possible miscalculation errors in input data individual variations in the timing of ovulation, and/or conception.
The information provided regarding pregnancy progress and fetal development is a guide through the weeks. It is not specific information for a specific individual but serves as a general guide only. As each pregnancy differs, any dates, weights, and lengths should be considered general information for interest only.
Our week-by-week guides use both standard and metric units of measure including pounds and kilograms.
What Is The Ultrasound Date And Why Is It Different From My Due Date
When a doctor performs an ultrasound, they write a report on the findings and include two estimated due dates. The first date is calculated using the date of the LMP. The second date is based on the ultrasound measurements. These dates are rarely the same.
When your doctor evaluates the ultrasound results, theyll determine whether or not these dates are in agreement. Your doctor probably wont change your due date unless its significantly different from your ultrasound date.
If you have more ultrasounds, each ultrasound report will contain a new due date based on the most recent measurements. An expected due date shouldnt be changed based on measurements from a second- or third-trimester ultrasound.
Due date estimations are more accurate earlier in pregnancy. Later ultrasounds are helpful in determining whether the fetus is growing well but not for determining the age of the fetus.
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How Are Due Dates Calculated
If you were having regular periods before pregnancy, your doctor will calculate your due date based off of your last menstrual period. This goes back to the fact that in order to get pregnant, your body ovulatedor released an eggroughly in the middle of your cycle and it was fertilized by sperm. That was the moment of conception.
To clarify, the gestational period of 40 weeks actually starts with the first day of your last period, which adds two weeks of time to the gestational period when your baby didnt even exist yetclear as mud, right?Is an ultrasound a more accurate way of finding out my due date?If you are having irregular cycles before getting pregnant, an ultrasound is usually done to find out how far along you are. An ultrasound is actually the most accurate way to date a pregnancy because all fetuses grow at a consistent rate during the first trimester and early second.
In other words, if your baby measures 9 weeks 2 days when you have your ultrasound, thats how far along you are, no matter when your last period was. Some women with regular cycles are confused about why their ultrasound due date doesnt match up with their last menstrual period due date. Ovulation isnt a perfect science and can happen earlier or later than the norm, which might shift your due date slightly.
When To Use Ultrasound To Determine Your Due Date
The American College of Obstetricians and Gynecologists recommends that ultrasound-established dates should take preference over menstrual dates when the discrepancy between ultrasound dating and LMP is Greater than 5 days before 9 0/7 weeks of gestation by LMP Greater than 7 days from 9 0/7 weeks to 15 6/7 weeks by LMP
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What If I Have Irregular Periods Or Long Cycles
Some women have cycles that are consistently longer than the average 28-day cycle. In these cases, a pregnancy wheel can still be used, but some simple calculations are necessary.
The second half of a womans menstrual cycle always lasts for 14 days. This is the time from ovulation to the next menstrual period. If your cycle is 35 days long, for example, then you probably ovulated on day 21.
Once you have a general idea of when you ovulated, you can use an adjusted LMP to find your due date with a pregnancy wheel.
For example, if your menstrual cycle is usually 35 days long and the first day of your LMP was November 1:
After you calculate your adjusted LMP date, simply mark it on the pregnancy wheel and then look at the date where the line crosses. That is your estimated due date.
Some pregnancy wheels may allow you to enter the date of conception which occurs within 72 hours of ovulation instead of the date of your LMP.
Can I Plan My Due Date
Whether you’re trying to avoid being very pregnant in the middle of summer or are a teacher who wants to maximize time off with your little one, you can try to time when you conceive in order to “plan” your due date. But even if you’re one of the lucky ones who’s able to get pregnant when she really wants to, just remember that you probably won’t be able to map out exactly when you’ll give birth to the day .
Still, you can try our Ovulation Calculator, which uses the date of your last menstrual period and your typical cycle length to discover the days you’re most likely to be fertile and increase your chances of conceiving.
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