Calculation of the date of birth by the duration of pregnancy. All methods of determining the estimated due date
Calculation of the due date
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Calculation of the due date
Pregnancy is the most desired and long-awaited event for any woman. Therefore, there is nothing surprising in the fact that long before the documentary confirmation (two cherished stripes on the test) of an "interesting" situation, each of us already feels changes in the body.
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After your gynecologist diagnoses pregnancy and determines the exact date of conception, it will take only 280 days or 10 obstetric months until the fetus is fully ripe. At the same time, one should not clearly focus on these indicators. They are very individual and depend on the physiological characteristics of a particular woman and on the environment in which she carried the child. It is known from practice that only 4% of babies are born clearly after 280 days. The rest, due to various factors, may be born earlier or later. In order to find out the approximate date of birth of your baby and determine the so-called gestational age, they are guided by the first day of the last menstruation.More calculators:
Do you have any more questions? read the answers below:
1. How accurate is the calculation for the day of conception
To understand the accuracy of the calculation, you need to decide on the calculation method. It's no secret that conception is possible only during the period of ovulation, during which a mature egg is released from the ovary. The duration of the menstrual cycle is an individual feature of every woman. On average, it can be from 28 to 35 days.
Ovulation occurs in the very middle of the menstrual cycle. The exact date can be determined by ultrasound, using special home tests for ovulation, or by measuring basal temperature. Some women have special signs on this day, by which she can determine that today is ovulation. It is on this day that conception occurs, which may not coincide with the day of physical intimacy, since sperm cells are able to maintain their viability in a woman's body for a week.
Knowing the day of conception, it is also a tribute to ovulation, it is quite easy to calculate the date of birth: you just need to add 266 days. This will be the estimated due date. The accuracy of these calculations will directly depend on the accuracy of determining the date of ovulation. If your cycle is not constant, and you are not sure about the date of conception, then this technique may give some error.
2. How to calculate the date of birth by menstruation
This method of calculating the expected date of birth is used in antenatal clinics. It is also called obstetric term. To determine the expected date of birth, you need to know the date of the start of the last menstrual period. This day is the starting point for the calculation. If the duration of the menstrual cycle is 28 days, then you can use the Negele formula, according to which the date of birth is calculated as follows: from the day of the beginning of the last menstrual period, three months are subtracted and seven days are added. You can also use another technique: 280 days are added to the date on which the first day of the last menstruation fell. According to scientific data, it is this period that is necessary for the ripening of the fetus.
But if your cycle is longer or irregular, then it will not be entirely correct to calculate the date of birth by menstruation. If the duration of the menstrual chicle exceeds 28 days, then labor is likely to come later, if on the contrary, then earlier. If the cycle is not regular, then this method of determining the expected date of birth will be rather indicative and cannot be used as a basic technique.
3. How to calculate the date of birth by the first stirring
Often, to determine the expected date of birth, they use such a landmark as the very first movement of the baby inside the abdomen, more precisely, the moment when the mother was able to feel the movement of her baby. Therefore, it is also called intuitive and experts consider it inaccurate. Moreover, if a woman gives birth for the first time, then she will most likely feel the first movement in the twentieth week of pregnancy. If a woman is about to give birth again, and she already knows what exactly she should feel, then the first movement of the fetus in most cases is felt at the eighteenth week. Now, in order to calculate the date of birth according to the first stirring, if the pregnancy is the first, it is necessary to count exactly 20 weeks from the date of the first stirring. If a second birth is coming, then only 18 weeks need to be counted.
As practice shows, quite often many primiparas and women giving birth again begin to feel the movement of their baby already at a period of 15-16 weeks. But there are also mothers who felt the first movement of their baby only at the period of 21-22 weeks.
Do not rush to apply this technique in practice to determine the expected date of birth, since in fact it is not known which category of expectant mothers you belong to.
4. How to calculate the date of birth by ultrasound
The most accurate method for determining the date of birth is considered to be diagnostics by ultrasound (by ultrasound), but it must be used very early, no later than the twelfth week. This method allows you to diagnose the gestational age with an accuracy of one day, thus indicating the approximate date of conception and, accordingly, the date of birth.
Later, the gestational age is determined by the size of the baby's head and limbs. But this conclusion does not allow us to accurately diagnose the expected date of birth, since each child develops completely individually, having a different weight not only at the moment of birth, but also during the period of its intrauterine development. Therefore, when determining the date of birth in the second trimester, an error of up to seven days appears, and an ultrasound scan in the third semester hardly makes it possible to judge the duration of pregnancy, based on the intrauterine dimensions of the baby.
Thus, in order to accurately calculate the date of birth by ultrasound, it is necessary to undergo an examination during the first three months of pregnancy. Otherwise, the intrauterine size of the baby will not allow you to accurately determine the date of the expected birth.
In this article:
The estimated date of birth begins to interest a woman from the first day she found out about her situation. The approximate birthday of a child can be calculated in several ways, but none of them can boast of 100% accuracy. Many factors can influence the pregnancy process, and labor is often premature or late.
What determines the term of delivery
Even in a healthy woman carrying a healthy baby, the date of birth may deviate from the estimated date and depends on:
- from whether she gives birth in or;
- from the duration of the menstrual cycle;
- from heredity and other individual characteristics of the mother;
- from the features of the intrauterine development of the baby;
- on how many children are in the womb.
In the presence of chronic diseases in a woman, impaired intrauterine development of the child, acute diseases or injuries during pregnancy, the term of delivery may significantly deviate from the planned date.
Methods for determining the date of birth
The most common methods for determining the expected due date are:
- by the date of the last menstruation;
- by the time of ovulation;
- by date of conception;
- by ultrasound;
- by the size of the uterus;
- by the first movement of the fetus.
Let's consider each in more detail.
By the date of the last menstruation
The date of birth by menstruation is the most common way to determine.
It has been used by obstetricians and gynecologists for many decades because:
- not all pregnant women know the time of the last ovulation or the date of conception during regular sex life, but everyone remembers when they had their last period;
- this is a fairly accurate method.
To determine the day of birth, you need to remember the first day of the last menstruation, add 1 year to this date, then subtract 3 months, and then add 1 week. The calculated date will be a guideline for the expected birth. Another way of determining: add 9 months and 1 week to the first day of the last menstruation.
By the time of ovulation or anticipated conception
The method of calculating the date of birth by the date of conception can be used with a planned pregnancy, when a woman has specially calculated the days of ovulation and knows them. It is during this period that conception occurs. To the first day of ovulation, add 266 days and calculate the date of delivery according to the calendar. This method is called embryonic.
By date of intercourse
This method is convenient to use with irregular or rare sexual activity. In this case, the woman knows which day in her life was decisive. It's very simple - 266 days are added to this date. This method is closer to embryonic. The dates of birth calculated in these two ways may differ by only a few days, because the dates of intercourse and conception often do not coincide. Not everyone knows that some sperm are able to live in a woman's body for up to 9 days, waiting in the wings.
By ultrasound
Using an ultrasound scan, the doctor can determine the approximate date of delivery, based on the established age of the fetus. Most accurately, this is established in the first trimester of pregnancy. In the future, there may be an error from several days to 3 weeks.
Largest uterus
The ancient medical method was the approximate determination of the duration of pregnancy and, accordingly, the expected birth by the size of the uterus. As in the previous case, you can more accurately determine the time of delivery in the early stages of pregnancy. In the future, the size of the uterus depends on many factors (the size of the fetus, the amount of water). In addition, this method is only suitable if there is 1 baby in the uterus.
At the first movement of the fetus
An ancient folk way of guessing the date of birth is to wiggle the baby. After the disappearance of menstruation, a woman could only suspect about the presence of pregnancy, but when the fetus began to move, this was an absolute sign.
The woman added 20 weeks to this date and could quite accurately guess the due date with minor errors. It should be borne in mind that multiparous are already familiar with the feeling of fetal movement in the uterus and they usually feel it 1-2 weeks earlier than primiparous.
Efficiency of calculations
The exact day of delivery cannot be determined, because the normal time for delivery is between 38 and 42 weeks of gestation. Thus, as many as 28 days can be considered the date of delivery "on time". However, in the normal course of pregnancy, different calculation methods are approximately the same and circle around the same date in the range of +/- 14 days.
Gynecologists still officially use the calculations for determining the possible day of birth by the last menstrual period, therefore this period is called obstetric. This method in about 20% of cases guesses the date of birth with an accuracy of +/- 5 days, and this is a fairly high percentage. The exact coincidence of the date of birth and obstetric term is about 5%.
How do the features of the menstrual cycle affect the date of birth?
Regardless of the duration of the menstrual cycle, the obstetrician-gynecologist applies the formula for calculating the due date by the date of the last menstruation. Accordingly, women with a short cycle and a long one will have the same due date. However, the date of ovulation is different for them, therefore, conception and due date will be different.
With a short menstrual cycle (24 days)
ovulation occurs on the tenth day. Fertilization takes place on the days of ovulation. Therefore, the actual term in women with a short cycle will be expected a week earlier. The due date is calculated using the following formula: the date of the first day of the last period plus 1 year and minus 3 months.
Long cycle (35 days) ovulation occurs on the twenty-first day. The birth will be a week later than the gynecologist calculated. A woman can calculate the date in this way: the date of the first day of the last period plus 1 year, minus 3 months and plus 14 days.
Calculate the date of birth with an irregular menstrual cycle with large jumps follows the classic formula.
When you can't use the obstetric calculation method
The obstetric method of determining the date of birth by the last menstrual period is the most common.
But it is not possible to use it in the following cases:
- when pregnancy occurs immediately after the previous birth, and there has been no menstruation yet;
- with severe menstrual irregularities, when the interval between periods can be more than several months, as is the case with menopause or various female diseases, for example, polycystic ovary or hormonal disorders.
What can be deviations from the terms
Carrying a child lasts 9 calendar months, or 10 lunar months (28 days each), or 280 days.
Childbirth is classified into urgent, premature and late:
- Childbirth at 38-42 weeks is a normal period. Statistically, 70% of mothers give birth in the 39-41 week range. Primiparas often give birth 1 week later than the normal due date. But with repeated births, on the contrary, women are more likely to give birth before 39 weeks.
- Childbirth after 42 weeks is late. In this case, the child is considered to be post-term. There are about 9% of such births.
- Childbirth before 38 weeks is premature. The viability of the baby depends on the gestational age at delivery. The closer this period is to normal, the better.
Everything is individual, and in case of premature birth, a completely healthy and mature baby can be born, more often this happens over a period of more than 35 weeks. If the baby is underweight - less than 2500 grams, he will be considered premature.
The second degree of prematurity is established when the term of delivery is from 32 to 35 weeks and the weight of the child is less than 2000 grams. However, he also has a lot of chances to "mature" and gain weight after birth without the use of life support hardware.
With premature birth from 28 to 31 weeks, the child will be with grade 3 prematurity and low body weight (from 1000 to 1500 grams). Such children are successfully nursed in perinatal centers.
When a baby is born at a period of 22-28 weeks, he will have a 4th degree of prematurity. The baby has extremely low body weight and undeveloped lungs. There is no surfactant substance that ensures free breathing of the child.
Previously, the fruit was considered viable from 700 grams, now - with a mass of 500 grams or more. Such children are cared for in intensive care units using special transparent plastic boxes - incubators, which provide the necessary temperature, humidity and sterility of the environment. The baby is connected to a ventilator, feeding is carried out intravenously or through a tube, the necessary drug therapy is provided.
A baby born earlier than 22 weeks will not be viable due to severe immaturity. Currently, medicine is not able to leave such babies.
Causes of premature birth
The total share of all preterm births accounts for about 10% of cases. The cause may be maternal or fetal abnormalities, or a combination of various factors.
The most common ones are:
- Social and household - smoking, alcohol abuse, drug use, stress, extreme physical activity, malnutrition and hypovitaminosis.
- Pathology of the uterus - the consequences of abortions, other operations on the uterus, hypoplasia, endometritis, endometriosis.
- Pathology of ongoing pregnancy - placental abruption, lack of water, premature rupture of amniotic fluid, inflammation of the membranes, multiple pregnancies,.
- Diseases of the mother - diabetes mellitus, hypertension, rheumatism, bronchial asthma, severe anemia, mental disorders, etc.
- Multiple anomalies in the development of a child, incompatible with life, at present, the latter is rarely the cause of premature birth, since women are trying to terminate pregnancy early for medical reasons.
In the presence of such risk factors, a woman should be especially careful, since she has a high risk of having a premature baby. She may have to spend some time saving.
Determining the expected due date is an important task. But in any case, the calculated period is approximate. It depends on many reasons. Therefore, with a long gestation period, a woman should listen to herself and expect childbirth, starting from the 37th week of pregnancy, or even earlier.
Helpful video on calculating due date
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Calculator PERIOD OF PREGNANCY
For many women, the feeling of an impending or already begun pregnancy occurs before the test shows two stripes - that is, even before the actual delay. Scientists cannot yet provide an explanation for these correct premonitions, but the concept of the Early Pregnancy Factor has already been introduced into the scientific lexicon, which describes the chemical reactions of the mother's body in response to a completed conception after only a few hours. Currently, there are already tests for the detection of the Early Factor hormone in the female body, but due to the significantly expensive cost, these tests are not produced on an industrial scale.
On average, childbirth occurs 10 obstetric months (280 days) after pregnancy, when the baby is ripe for birth. However, it should be noted that 280 days is a conditional number of days of bearing a child. All female organisms are different, and all babies mature differently in their mother's tummy. Someone will need 280 days, while others will be "ready" in 240 days. Only 2% of newborns are born on a precisely calculated day. Most of the kids are two weeks earlier, or a few days later than the appointed time. The duration of pregnancy and childbirth is calculated based on the date of the start of the last menstrual period.
If we take into account all the changes that occur with the baby almost every day during pregnancy, and especially the first trimester, then in general these processes can be compared in importance and complexity, in depth with the birth of a new universe. Every day of a little crumbs inside you is not just a step, it is a huge leap forward, a breakthrough. The birth of a new life, despite the scale of its accomplishments, does not require any external efforts for itself .. everything happens under the cover of secrecy. After all, the woman herself learns that conception has occurred only after some time. Thanks to modern technology, scientists have managed to learn a little about the great mystery of birth - that where EVERYTHING begins. Enter your data and flip through the pages of the calendar of the development of human life throughout pregnancy. Believe me, amazing discoveries await you!
Calculator
The question of how to determine the date of birth often causes discussion and controversy among pregnant women. The difference between your own calculations, the terms that are set during an ultrasound examination and those that the doctor writes on your card is completely confusing. Specifically, in order to make life a little easier for pregnant women, we have developed a program that independently calculates the estimated date of birth. Now you don't have to visit a doctor or bother with mathematical calculations, just to calculate the date of birth of your baby, you just need to enter in the required column of the calculator the number when you started your last menstruation.
The Negele Formula is a two-step task.
The program that allows you to calculate the date of birth is based on the Negele formula, named after the German obstetrician who first proposed using this simple method of calculation. It is known that pregnancy lasts an average of 40 weeks from the beginning of the last menstrual period or 38 from the moment of conception. Negele simplified the calculations by reducing them to a few simple arithmetic operations - remember the date of the onset of menstruation prior to pregnancy and subtract 3 months. You need to add 7 days to the resulting figure - this number is the very date of birth.
The question often arises - why should the date of birth be calculated based on the date of the last menstruation? This tradition, generally accepted in obstetrics, is justified, because not all women know exactly the day of ovulation, while most keep a calendar of menstruation. The bewilderment is also natural - after all, in the first, so-called "weeks of pregnancy", conception has not even occurred. Yes, this is true, and this period refers to the gestational age conditionally, for the convenience of obstetricians-gynecologists, according to the standards. The fetus begins its existence when about 14 days of pregnancy are already behind. If you reliably know the number when fertilization occurred, you can calculate the date of birth yourself, adding 266 days - this is the average gestation period.
Is deviation from the calculated date the norm?
It is worth noting that the estimated due date is nothing more than a guideline for you. In fact, about 17% of women give birth on day X, the remaining 83% a little earlier or later. No specialist can predict the onset of labor. Moreover, normal, urgent childbirth, that is, childbirth that occurred in physiological terms, is considered to be those that happened from 38 to 42 weeks of pregnancy. Unpredictable overmaturity or undermaturity of pregnancy is not uncommon. Abnormalities in fetal development, pathological processes in the maternal body, stressful situations, hereditary factors and many other reasons can provoke the onset of premature labor. Therefore, it is very important to understand that calculating the date of birth is a very conditional concept, regardless of the method used.
However, there is some regularity, taking into account which it is possible to assume the development of the situation in a healthy pregnancy - the longer the monthly cycle, the longer the pregnancy lasts. Before you determine the date of birth, taking into account your individual characteristics, remember the length of your menstrual cycle - from the first day of some menstruation to the first day of others. If your cycle is longer than the standard 28 days, your pregnancy is likely to last more than 40 weeks, and vice versa. Keep in mind that we are talking about postponing the estimated due date by no more than 5 days.
The calculator will help you calculate the date of birth by menstruation as accurately as possible, but you should remember that the data obtained during a medical examination are of decisive importance as more reliable. The reason for this approach is that menstruation can be easily confused with bleeding, which opened after conception and stopped spontaneously. Also, when examined in the third trimester or ultrasound of the uterus, the doctor can observe the degree of maturity of the placenta, the position of the fetal head in relation to the entrance to the pelvis, opening of the cervix, signs of full-term fetus and many other important data. By all these parameters, one can judge the readiness of the fetus and uterus for childbirth and the likelihood of their early onset. In addition, based on the size and proportions of the fetus during ultrasound examination, the doctor sets the age of the fetus in accordance with.
How to find out the due date? On the method of calculating the date of birth
For calculating the estimated due date obstetricians-gynecologists have a very convenient and uncomplicated formula: 9 months and 7 days are added to the date of the first day of the last menstruation. And you can calculate it even easier - from the first day of the last menstruation, they count back 3 months and add 7 to the resulting number.
Estimated due date = date of first day of last menstrual period + 9 months + 7 days.
Estimated due date = date of first day of last menstrual period - 3 months + 7 days.
But these terms are typical for the average woman with an average 28-day menstrual cycle and ovulation on the 14-15th day of the cycle.
The average pregnancy lasts 266 days (38 weeks) from the day of conception, or 280 days (40 weeks) from the first day of your last menstrual period. If the menstrual cycle of the expectant mother is shorter or longer than the average 28 days, or ovulation did not occur on the 14-15th day of the cycle, then the pregnancy may also be longer or shorter. Therefore, it is generally accepted that 280 days is the approximate number of days of pregnancy and a baby can be born between the 266th and 294th days (38-42 weeks) of pregnancy.
Calculation of the date of birth by the day of conception is not an accurate method of determining the due date. Even if you know for sure the day when sexual intercourse occurred, this does not mean that it was on this day that conception occurred, since sperm cells are able to remain active in the vagina for up to several days.
How else can you determine the gestational age and calculate the due date?
Determining the duration of pregnancy using ultrasound
In the early stages, before 12 weeks of pregnancy, you can calculate the date of birth using an ultrasound scan quite accurately. For long periods of time, this is often difficult due to the fact that each child grows at its own pace. Namely, such indicators as the size of different parts of the fetal body are the basis for calculating the gestational age.
Determining the duration of pregnancy during a gynecological examination
During pregnancy, the uterus begins to gradually increase in size and takes on a spherical shape. With a gynecological examination up to 12 weeks, the doctor can determine the approximate duration of pregnancy by the size of the uterus. For periods of more than 16 weeks, when the uterus extends beyond the bosom, the period can be determined by the height of the fundus of the uterus during examination of the abdomen. Naturally, this method of determining the gestational age is not accurate.
Determining the duration of pregnancy by the first movement of the child
Another auxiliary method for determining the duration of pregnancy and calculating the date of birth is by perturbation. Despite the fact that the child begins to make movements quite early, the mother can only feel them when the baby reaches a certain weight. This usually occurs in primiparas at 18-20 weeks of gestation, and in multiparous ones 2 weeks earlier. However, some women claim that they feel perturbations as early as 14 weeks and sometimes earlier.
Using all of the above methods, you can more or less accurately determine the gestational age, but the due date will still be approximate. This means that the probability of giving birth on PDD +/- 3 days is about 70%. Do not forget that the child's readiness for extrauterine life also affects the date of birth. Some babies of so-called morpho-functional maturity may reach 38 weeks, while others may reach 41.