Due date and pregnancy
Calculate your due date: How to find your baby's due date
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First day of my last period
BabyCenter's Due Date Calculator
Use our pregnancy due date calculator by plugging in either the date of your last menstrual cycle or the date you know you conceived. The calculator will do the rest.
How is my due date calculated?
There are several ways your due date is determined. If you happen to know the day you conceived, you can count 38 weeks from that day to find your due date. (Human gestation takes about 38 weeks.)
But very few expectant moms know exactly when they conceived. Even if you only had sex once during your fertile period, you wouldn't conceive on that day unless you happen to be ovulating. Sperm can live for up to five days inside your fallopian tubes. So, it could be up to five days after you have sex that you release an egg (ovulate) and it gets fertilized by a waiting sperm. That's the day you conceive.
So, without knowing the day of conception, how does anyone determine a due date?
First day of your last period
The most common way to calculate your pregnancy due date is by counting 40 weeks from the first day of your last menstrual period (LMP). And that's how most healthcare providers do it.
If your menstrual cycle length is the average length (28-day cycle), your menstrual cycle probably started about two weeks before you conceived. This explains why pregnancies are said to last 40 weeks instead of 38 weeks.
This method doesn't take into account how long your menstrual cycle actually is or when you think you might have conceived. But generally speaking, women typically ovulate about two weeks after their menstrual cycle starts. And women are more likely to know when their last period started than the day they ovulated.
Conception date
If you do happen to know precisely when you conceived – say, if you were using an ovulation predictor kit or tracking your ovulation symptoms – you can calculate your pregnancy due date based on your conception date. Just choose that calculation method from the pulldown above and put in your date.
Note: Again, you don't necessarily conceive on the day you have sex.
IVF transfer date
If you conceived through IVF, you can calculate your due date using your IVF transfer date. If you had a Day 5 embryo transfer, count 261 days from your transfer date. If you had a Day 3 embryo transfer, count 263 days.
Can my due date change?
Your healthcare provider might revise your due date if your baby is measured during a first trimester ultrasound scan and found to be much bigger or smaller than expected for gestational age. This is more likely to happen if you have an irregular menstrual cycle length that makes it hard to pinpoint the date of conception.
Your healthcare provider will measure your baby during that ultrasound exam to figure out how far along your baby is and then provide you with a new due date.
What if I already know my due date?
If you already know your due date, you can use this calculator to see your pregnancy timeline. It will tell you when you'll hit various milestones, and when you may be due for prenatal tests and prenatal visits. You'll also find what your baby's sign and birthstone will probably be and which famous people were born on your due date.
How likely am I to give birth on my due date?
Of course, a due date calculation is always approximate, whether it's from our tool or from your doctor or midwife. Only 1 in 20 women delivers on their due date. You're just as likely to go into labor any day during the two weeks before or after.
Want more information about how the weeks, months, and trimesters of pregnancy are counted? See our pregnancy timing chart.
How soon can I take a pregnancy test?
With all this talk about pregnancy due dates, you may be wondering when you can take a pregnancy test. To ensure you get the most accurate reading, it's best to wait a few days after your missed period to take a pregnancy test.
At-home urine tests measure the amount of hCG (human Chorionic Gonadotropin) present in your body. If you take a pregnancy test before you miss your period, you may not get an accurate result, despite what some tests advertise.
If you're getting a blood test in your provider's office, you may get results sooner. These tests also measure the amount of hCG in your bloodstream, but they're more sensitive than at-home urine tests. Blood tests may be able to detect pregnancy six to eight days after ovulation.
Read more
- Your pregnancy, week by week
- Your first trimester pregnancy checklist
- Pregnancy Weight Gain Calculator
- Ovulation Calculator
- See all tools
Pregnancy tests: How soon can you get a positive pregnancy test?
Pregnancy tests work by detecting the presence of a hormone called human chorionic gonadotropin (hCG) in your urine. Some home pregnancy tests claim they're sensitive enough to give a positive result as early as five days before you would expect your next period. But you're more likely to get an accurate result (and avoid a false negative pregnancy test) if you wait to test until after the first day of your missed period.
How soon can you take a pregnancy test?
You're more likely to get an accurate result if you wait a few days to a week after you expect your period before taking a pregnancy test.
Some home pregnancy tests claim they're sensitive enough to give you a positive result as early as five days before you would expect your next period. And some women will have produced enough hCG to get a positive result at that point. So if you're anxious to know, go ahead and try it. If you get a negative result, you can just wait and test again later if you still haven't gotten your period.
Most home pregnancy tests claim to be accurate on the day you miss your period, but even then, the amount of hCG in the urine at this time can vary a great deal from one woman to another.
If you test too soon, you may get a false negative pregnancy test (a negative result even if you are pregnant) or an unclear result like a faint line on a pregnancy test.
How do pregnancy tests work?
Home pregnancy tests tell if you're pregnant or not by detecting the presence of hCG in your urine.
This hormone is produced by cells that will develop into the placenta. It first enters your bloodstream when the fertilized egg starts to implant in the lining of your uterus, as early as six days after fertilization.
The amount of hCG in your body then increases rapidly over the next few weeks, often doubling every two days or so. When a pregnancy test detects the hormone in your urine, it shows a positive result.
Home pregnancy tests are now about 99 percent accurate, when done correctly. And there's no reason to pay more for one test over another. As long as a test isn't expired, it should be equally as accurate as another test.
What will differ between tests is their sensitivity. Detecting hCG in the urine of someone 6 months pregnant (when there's plenty of hCG) versus 6 days past ovulation (when there's a very small amount of hCG) are two very different tasks. The ability of a test to pick up small amounts of hCG in your urine depends on the sensitivity of the test.
It's not always easy to tell which tests are the most sensitive. New products come out frequently, and manufacturers can make improvements at any time.
But some package inserts provide information about a test's sensitivity – that is, they report the lowest concentration of hCG in milli-International Units per milliliter (mIU/ml) of urine that the test can detect. For example, a pregnancy test that claims to be able to detect hCG at 20 mIU/ml should be more sensitive than one that claims to detect it at 50 mIU/ml.
How do I use a home pregnancy test?
For best results when using a home pregnancy test:
- Make sure the test is current. Check the expiration date on the package, especially if you've had it for a while. If you've been storing the test anywhere that gets moist or warm, like the bathroom, it may have deteriorated. If that's the case, it's better to throw it away and get a new one.
- Test first thing in the morning. Your urine is most concentrated when you first get up, so hCG levels (if present) will be easier to detect at that time.
- Read the directions carefully. Directions vary with different brands. Some require you to urinate in a cup and then use the dropper provided to place a small sample in the testing well. With others, you can pee directly onto the testing device. And some let you do either.
The tests also vary in how they display the results. For example, some show pink or blue lines on the test strip, while others reveal a red plus or minus sign in a window. "Digital" tests tell you in words whether you're pregnant. Most have a control indicator (often a second line or symbol) to indicate whether the test is valid.
It may take up to 10 minutes to see results. If the control indicator doesn't show up properly, the test may be faulty. If this happens, you can usually call the manufacturer and have them send you a new one (though it probably won't arrive soon enough to use that same month).
If you have questions about how to use a test, call the manufacturer's toll-free number on the package instructions.
If the test shows a negative or a faintly positive result, wait another few days or a week and try again if you still haven't gotten your period. One possibility is that you ovulated later in your cycle than you thought and took the test too early to get a positive result.
Don't assume that one negative result means you're not pregnant. The amount of hCG produced is different for every woman and varies with each pregnancy. If you suspect that you're pregnant (for instance, if you're having early pregnancy symptoms) and still have a negative test, repeat a urine pregnancy test in a week if you still haven't gotten your period.
If you still haven't gotten either your period or a positive result two weeks or so after you would expect it, contact your healthcare provider.
False positive pregnancy tests
A false positive pregnancy test means that you get a positive result, but aren't pregnant. These are uncommon, but they can happen under certain circumstances:
- You had a miscarriage or a pregnancy termination in the previous eight weeks or have a molar pregnancy.
- You've taken a fertility drug containing hCG (used to induce ovulation in fertility treatments).
- You have a rare medical condition, such as an hCG-secreting tumor.
- You're using an expired or faulty test.
- You're experiencing menopause or perimenopause.
If you have an early positive result and then get your period soon after, you may have had what's sometimes called a chemical pregnancy. This means a fertilized egg implanted in your uterus and developed just enough to start producing hCG, but then stopped developing for some reason. This form of early pregnancy loss usually happens when the fertilized egg has defects that prevent it from growing normally.
After a chemical pregnancy, your period may be a little heavier and a few days later than usual.
Note: An ectopic pregnancy usually results in a positive pregnancy test, even though these pregnancies show slower hCG rises. No matter what result you get from a pregnancy test, call your healthcare provider right away if you:
- Feel dizzy or faint.
- Have abdominal pain (especially a sharp or stabbing pain in your abdomen or on one side of your pelvis).
- Have abnormal bleeding.
Pregnancy blood tests
Most healthcare providers use a urine pregnancy test, just as you would at home – but your provider may use a blood test instead. It takes anywhere from an hour to a day or more to get the results.
There are two types of pregnancy blood tests:
- A qualitative hCG blood test simply detects whether there is hCG in your blood. It will give pregnancy results at about the same time as a urine test. The results return as "positive" or "negative."
- A quantitative blood test (beta hCG test or serum test) measures the exact amount of hCG in your blood. The results return as a number. This test is very accurate. It can detect hCG as early as six to eight days after ovulation, about a week before your period is due. It takes longer to get results from a quantitative blood test, though.
Some testing companies will let you pay online and then go to a lab and have a blood sample taken. The testing company will provide you with your result the next day by phone or online. These tests start at about $40. If you decide to use one of these companies rather than going through your healthcare provider, be sure to find out which type of blood test they're using.
What to do after a positive pregnancy test
Some women take more than one pregnancy test (or several) just to be sure – but that's not necessary. Once you've gotten a positive pregnancy test, call your healthcare provider to set up a prenatal visit or to discuss your options if you're uncertain about continuing the pregnancy.
For prenatal care, providers typically schedule the visit for when you're at least 8 weeks pregnant, but it varies. Some will see you sooner, particularly if you have a medical condition or have had problems with a pregnancy in the past. It's especially important to see a provider soon if you're having nausea and vomiting, vaginal bleeding, or abdominal pain.
If you don't already have a family doctor, ob-gyn, or midwife, do some research and ask for recommendations. But don't delay your care while searching for a good fit, because you can always switch providers later. At your first prenatal visit, your provider will take your health history, explain your options, and more.
Learn more:
- I'm pregnant – now what?
- Implantation bleeding
- Pregnancy symptoms
How to correctly calculate the gestational age and determine the date of delivery
It often comes as a surprise to first-time pregnant women that in obstetrics the gestational age is determined not in months, but in weeks. But the surprises do not end there - the fact is that the obstetric period is calculated not from conception, but from the first day of the last menstruation.
In fact, pregnancy occurs two weeks after the start of the obstetric period, at the time of ovulation, when the sperm meets the egg. Thus, the age of the embryo, or gestational age, differs from the obstetric one by 2 weeks down.
How long does pregnancy last?
The obstetric term of a term pregnancy is 40 weeks, or 280 days. It is on the basis of the obstetric gestational age that the doctor will prescribe tests and examinations for you, determine the date of maternity leave and calculate the EDD (estimated date of birth).
Doctors use the Negele formula to calculate the EDD. According to this formula, if we add nine months and seven days to the first day of the last menstruation, we get the estimated date of birth.
Unfortunately, determining the gestational age from the first day of the last menstrual period is not a very accurate method. It is well suited for women with a stable 28-day cycle, but if your cycle is slightly longer or shorter, then the date of ovulation shifts, respectively, and the actual obstetric gestational age will differ from the established one.
The most accurate way to calculate the EDD is to add 266 days to the date of the last ovulation (if you know it).
How to confirm pregnancy, determine the duration of pregnancy and the date of delivery
By itself, a delay in the start of a new menstrual cycle does not necessarily indicate pregnancy - failures can be explained by diseases, excessive physical exertion or stress. Pregnancy must be confirmed with an hCG test or examination on a gynecological chair. 1) Blood test for hCG cycle or the woman will feel the first symptoms. Also, an analysis of the level of hCG in the blood allows you to determine the gestational age with an accuracy of about two weeks.
2) Home pregnancy test
Home pregnancy tests also work by measuring hCG levels, but they are less sensitive than blood tests. The most modern of them can not only confirm the presence of pregnancy a few days before the delay, but also indicate (not too accurately) an approximate date.
Tests of the old generation will show a more or less accurate result only after a delay, that is, after 2-4 weeks from conception.
3) Gynecological examination
A qualified gynecologist-obstetrician can diagnose pregnancy during an examination starting 3-4 weeks after conception, focusing on changes in the shape and size of the uterus, as well as other signs.
4) Ultrasound
Ultrasound is the most accurate way to diagnose pregnancy. With the help of ultrasound with a transvaginal sensor, it is possible to determine the presence of a fetal egg in the uterus already 1-2 weeks after conception (3-4 obstetric weeks), but fetal heartbeats can only be detected for a period of 5-6 obstetric weeks. It is possible to determine the gestational age with high accuracy (up to 2-3 days!) With the help of ultrasound only from 6-7 weeks.
If the delay, as well as the result of an hCG test or blood test, indicate that you will soon become a mother, do not rush to get an ultrasound right away. Wait another 2-3 weeks, then by ultrasound you will not only be accurately determined by the period, but will also be allowed to listen to the baby's heartbeat.
If you did not do an early ultrasound to confirm pregnancy, then for the first time you will encounter this study at the 10-14th week. At the same time, the exact gestational age and PDR will be established or corrected for you. During pregnancy, you will need to undergo such an examination at least twice more. This will happen at 20-24 and 30-34 weeks. However, it is worth saying that ultrasound in the 2nd and 3rd trimesters may have an error in determining the gestational age. The PDR established according to them may differ from the real one by 2-3 weeks. That is why it is so important not to miss the first screening and do an ultrasound on time.
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Angarsk Perinatal Center: Pregnancy Calendar
Regardless of whether this is your first pregnancy or you already have a child and are expecting another one, an exciting period of life is coming for you. You began to feel the birth and development of a new life within yourself.
Due date calculation
In most cases, women do not know the exact date of conception, but they can tell exactly when the last menstrual cycle began. This is the point from which pregnancy is usually counted. For most women, the most likely period of fertilization (ovulation) lies in the middle of their monthly cycle, in other words, two weeks before the start of the next menstrual cycle.
Based on this date, pregnancy lasts about 280 days, or 40 weeks, from the start of the last menstrual period. So you can get your estimated due date by adding 280 days to the date you started bleeding in your last cycle. The same result can be obtained by adding 7 days to the date of the last menstrual period and subtracting 3 months. For example, if your last period started on February 20, then your due date is expected to be November 27.
This calculation of pregnancy determines the so-called gestational, or menstrual, age of the fetus. It is on this “calendar” that doctors and nurses will track the development of the fetus. Gestational age is different from ovulation, or fertilization, age, which is two weeks earlier and is counted from the actual date of conception.
Many people calculate their pregnancy in weeks. This is the easiest and most convenient way to avoid confusion. For example, if your doctor says that you are 10 weeks pregnant (remember that the count is from the start of your last menstrual period), then you conceived about 8 weeks ago and will go into labor in 30 weeks because your total pregnancy is 40 weeks.
There is also a large unit of measurement - trimester. The trimesters divide the pregnancy into three phases. Each such phase, lasting 13 weeks, has its own characteristics.
You may also have heard of another unit of time, the lunar month. It corresponds to the cycle of lunar phases and is 28 days. The full gestation period, equal to 280 days, is 10 lunar months.
The calendar is based on a 42-week pregnancy schedule. The expected time of labor (ETD) is at the end of the 40th week. This way you will know the age of the developing fetus at any point during the pregnancy.
It is important to understand that the RID is an estimate and not a precise date. Only 1 in 20 women give birth on the exact day of their OBD, and 90 percent of women give birth a week earlier or a week later. Therefore, one cannot rely on the date of the OVR. It may turn out that it will come, and the child will not be born for some time. Consider this date as a guideline - a deadline for which you must prepare.
There is no fundamental difference how to count the time of pregnancy. Still, the process will not go faster. It will continue as long as nature allotted. After all, a miracle happens - a new life grows and develops in your body!
Your menstrual cycle
You estimate that your menstrual cycle probably ends at the beginning of the second week of pregnancy or a few days earlier. The usual interval between periods is 28 days, but they can occur after 21 and even after 35 days , and there is nothing abnormal in this. Actually menstruation in most cases lasts from 4 to 6 days. Discharge from the uterus is a mixture of sloughed uterine mucosa and blood. Clotted blood clots may also appear. On average, during menstruation, a woman loses 25-60 ml of blood. Blood loss can be different for different women, and for one woman it can change from one cycle to another.
Two important biological cycles occur almost simultaneously in a woman's body. As a result of the ovulation cycle (ovulation), a mature egg appears, ready for fertilization, and during the endometrial cycle, the uterine wall is prepared for implantation of the fertilized cell. Both cycles are closely related to each other because endometrial changes are regulated by hormones that are released in the ovary.
The normal alternation of the ovulation and menstrual cycles (with the production of one egg for fertilization) is the rule, not the exception. Some women experience uneven cycles of egg production. Such cycles can take place without ovulation. This is quite rare compared to regular and predictable menstrual cycles and hormonal changes.
Your body produces many hormones, including follicle stimulating hormone (FSH) and luteinizing hormone (LH) produced by the pituitary gland, as well as estrogen, progesterone and androgens (testosterone) produced by the ovary.
The natural purpose of the ovulation cycle is to produce an egg for fertilization. The body of a newly born girl contains about 2 million eggs. Their number is reduced to about 400 thousand by the beginning of puberty. But the maximum number of eggs is formed even before birth. When a fetus is only 5 months old (4 months before birth), it contains approximately 6.8 million eggs.
During the ovulation cycle, 20 or more follicles may begin the process leading to ovulation. And only one of them, bursting, can turn into a mature egg. Before the onset of ovulation, this follicle approaches the wall of the ovary, which becomes progressively thinner. At the time of ovulation, an egg is formed at the site of the burst follicle. The place of rupture of the follicle on the wall of the ovary is called the stigma.
Some women (about 25 percent) experience lower abdominal pain or discomfort on the day of ovulation or the next day. It is believed that they are caused by irritation of the ovary with fluid or blood of the follicle when it bursts. Pain is not necessarily felt with every cycle. By the presence or absence of this symptom, one can judge whether ovulation has occurred or not.
Most often, a woman becomes pregnant in the middle of the menstrual cycle, on the 12-14th day from the beginning of the last menstruation.