It is useful for a woman planning to become a mother to learn how to calculate the approximate date of birth based on the known date of her last menstruation. These calculations, of course, will not be absolutely accurate, but knowing even the estimated moment of birth will allow you to calmly prepare for the upcoming process.
Calmness and poise are very valuable qualities for a pregnant woman; they should be armed and guided from the first to the last gestational week. The following material is about how the date of birth is calculated based on the last menstruation.
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Based on the average duration of pregnancy (40 weeks), it is not difficult to calculate the date of birth based on the last menstrual period. To do this, count 40 weeks ahead according to the calendar from the start date of menstruation.
In world obstetric practice, a quick method is used to calculate the duration of pregnancy and, accordingly, childbirth from this starting point - the date of the last menstruation. The timing of pregnancy determined by this method is called obstetric. They cannot be considered accurate, if only because no one can predict how many weeks the pregnancy will last - 36 or 42.
Obstetric calendar
The starting point in the calculation formula is the first day of the last menstruation:
- from the 1st day of the last menstruation, you need to count back 3 months according to the calendar;
- add 7 days to the resulting date.
- My last period started on May 6th.
- We count from May 6 3 months ago - we get February 6.
- We add 7 days to February 6 and we get February 13.
- The estimated date of birth, as calculated by menstruation, is February 13th.
This simplest method of calculation is called Naegele's formula, and its reliability correlates with the length of the menstrual cycle. If the cycle is too long or irregular, errors in calculations are inevitable.
What affects the due date?
The opinion of Western experts regarding myths regarding the influence of certain factors on the date of birth is interesting. They conducted a study in which they tested urine daily to measure hormone levels. Thanks to daily monitoring, the dates of fertilization of the subjects were accurately determined and the duration of gestation was calculated with maximum accuracy. As a result (after delivery), it turned out that the timing in some cases differed from that calculated for as much as 5 weeks, although the pregnant women were in the same conditions.
The most well-known factors influencing the duration of gestation and date of birth:
- duration of monthly cycles - it is believed that the longer they are, the later the birth will occur;
- hereditary predisposition - in families where women carry children, this feature is passed on from generation to generation;
- dynamics of intrauterine development - if the fetus develops “according to plan”, gains weight and height on time, the date of birth may coincide with the calculation based on the last menstruation.
Experts have criticized the myth about the influence of spicy food on the due date - if it is calculated by the date of menstruation, and labor does not occur, there is no need to “accelerate” it by eating spicy seasonings, as about 20% of pregnant American women do. In this way they try to increase peristalsis (wave-like contraction of the walls of the stomach or intestines) and provoke uterine contractions, but this method is not scientifically substantiated.
The statement that the first birth is usually post-term is also incorrect. Medical research data suggests that the first birth often occurs earlier than the date that the LCD was able to determine from the last menstruation.
The order of births does not affect their timeliness.
Is it possible to determine accurately and what is the error?
Despite the fact that the Naegele formula is considered an approximate way to find out the date of birth based on the last menstruation, a considerable number of women on forums claim that their children were born almost exactly at the time calculated by the doctor +/- 1-2 days. In this case, can this method of calculation be considered accurate if statistics indicate only 5% of matches between the date of birth and the one that could be calculated using the date of the last menstruation?
Most doctors generally propose to cancel the indication of the exact date of delivery in order to save future parents from completely unnecessary worries about the “wrongness” of the onset of true labor. This, according to experts, gives nothing but an extra reason for a stressful situation for the expectant mother and her relatives.
As studies have shown, under the same gestation conditions, the time of onset of labor in different women may differ by 5 or even 6 weeks, that is, by 1.5 months.
How to calculate the due date in other ways?
If in doubt about the date of the last menstruation, the due date can be calculated using such methods as ultrasound examination, calculation based on gynecological examination, the appearance of the first fetal movements, and others. None of the listed methods guarantees the accuracy of the calculations.
How to find out by ultrasound?
When a woman is in the early stages of pregnancy (11-12 weeks), the doctor determines the PDR based on fetal parameters:
- the size of the fertilized egg and embryo is visualized already at 4-5 weeks;
- coccygeal-parietal size (KTR) - the length of the fetus from the head to the coccyx;
- the size of the baby’s limbs, head and tummy, which develop approximately the same in all children up to 12 weeks.
Based on these parameters, the gestational age is determined, and based on this, the due date can be calculated, taking into account the approximate date of conception (usually 7-14 days from the first day of the last menstruation).
Calculation based on inspection
Examinations when registering a woman after a missed period also make it possible to calculate the date of birth. In this case, such parameters as (the most reliable) and the size of the uterus, determined during a gynecological examination, are taken into account. This is one of the oldest ways to determine the duration of pregnancy in the earliest stages (and, accordingly, childbirth).
By 5 weeks, the uterus softens, becomes rounded and slightly increases in size. This is exactly how it is felt during a two-handed examination, when an obstetrician-gynecologist examines the condition of the cervix through the vagina with one hand, and palpates the abdomen with the other, trying to detect an enlarged and rounded uterus.
After the 12th week, the method of determining the period by examination is not used, since changes in the uterus vary depending on several reasons:
- the structure of the pelvis of the expectant mother;
- the amount of amniotic fluid in the fertilized egg (, and normal);
- fruit size.
When receiving examination data that differs from calculations based on ultrasound or the date of the last regulations, preference when recording in the pregnant woman’s chart is given to the latter.
Manual examination of a pregnant woman
How to count from the first movement?
Today it is not recommended to calculate the maximum fetal life span based on the appearance of fetal movements. Previously, the calculation was simple: 20 weeks were added to the date when the child first moved and the expected date of birth was obtained. Long-term observations have shown the complete inconsistency of this method, since the onset of fetal movements varies markedly among different women:
- some expectant mothers begin to “hear” the baby at 15-16 weeks;
- in others, movements begin after 20 weeks;
- working mothers, who are in constant movement and bustle, may not notice and miss the beginning of the first push;
- future mothers in labor, sitting at home and listening to every sound inside themselves, can mistake intestinal peristalsis for movements.
Even mothers who have given birth repeatedly are not immune from imaginary sensations, so it is not advisable to calculate the date of birth based on movements.
If the date of conception is known, and this cannot always be determined with high accuracy, calculating the date of birth is as simple as using the date of menstruation. To do this, you just need to count 40 weeks forward or 3 months ago according to the calendar from the day of conception. But this calculation cannot be called absolutely accurate, since the actual duration of pregnancy is impossible to predict.
Child development calendar
While waiting for the birth, it is interesting to follow how the baby develops, how he prepares for birth, according to the fetal development calendar. The calendar is compiled based on many years of observations of intrauterine development using various diagnostic tools.
| Term | Fetal condition |
|---|---|
| 1st trimester | By the age of 2 weeks, the fetus has the size of a grain of sand (0.35-1.00 mm), but already receives biochemical support, respiration and nutrition from the so-called extraembryonic organs - amnion, chorion and yolk sac. At 3 weeks, the heart, central nervous system, rudiments of bones and muscles, ears and eyes are formed, the growth of the embryo is 1.5 mm. 4-8 weeks are the most important and vulnerable period, subject to harmful influences. The nervous system and other organs are actively forming, and the heart begins to beat. The weight of the embryo reaches 3 g, the parietal-sacral size is 14-20 mm. At 8 weeks, the development period is called fetal, and the embryo becomes a fetus. His skin is still transparent, with blood vessels visible underneath. The formation of the external genitalia begins and the tail disappears. At 10 weeks, the fetus already looks like a miniature copy of a human, albeit with a disproportionately large head and small limbs. Over the last 3 weeks, growth has almost doubled - to 60 mm according to CTE, weight - 8-14 g. |
| 2nd trimester | The baby’s facial features quickly take shape, “germinal fluff” (the basis of future fingerprints), fluff appears on the brow ridges and on the head. The first taste sensations arise - the fetus reacts to bitter, sour and sweet substances dissolved in the amniotic fluid by swallowing movements. He can yawn, suck his thumb and even tumble, but his mother doesn’t feel it yet. When the obstetrician palpates the mother's belly, the fetus reacts - frowns and turns its head. By the 16th week, the fetus acquires the following parameters: CTE - 108-116 mm, weight - 80-110 g. By the 20th week, the baby's movements become more active and noticeable by the mother. He gains 10 g per day in weight and grows in length. At 22 weeks, it weighs 530-600 g, body height is 21 cm, stores adipose tissue under the skin, becoming plump and less nimble than before. |
| 3rd trimester | At 28 weeks, the fetus reacts to external sounds (music, mother’s voice, etc.). “Trains” its lungs by swallowing amniotic fluid and making “breathing movements” with the chest. His total height (from head to heels) is 38 cm, weight is 1.3 - 1.4 kg. By 30 weeks, wrinkles disappear from the baby’s face, there is already a decent amount of “hair” on the head, which becomes proportional to the body, weight reaches 1.8 kg, and total height is 42 cm. At 31 weeks, the baby’s immune system intensively develops and subcutaneous fat increases. Surfactant appears in the lungs - a substance that will prevent the baby’s lungs from sticking together after birth and ensure their functioning. The baby’s weight is approaching 2 kg, and his full height is up to 43 cm. 34 weeks – growth by leaps and bounds. Most babies by this time turn over in the uterus head down. Weight is approaching 2.75 kg, height – 46 cm. At 36 weeks, the pregnancy status is defined as full term, and delivery is expected any day now. The baby's skin is cleared of vellus hair, the hair on the head has grown to 1-2 cm, the nails have grown higher than the fingertips. Meconium, a black-green substance that is the original feces, accumulates in the baby’s intestines. After birth, it will immediately leave the child’s body. In boys, the testicles have already descended into the scrotum; this will need to be checked immediately after the baby is born. The child's weight reaches 3.1 kg, height is close to 50 cm. |
The baby development calendar shows that calculating the date of birth using menstruation can be very conditional - by the 36th week the baby is ready for birth, but can remain in the womb for several more weeks. The reasons for the baby’s continued stay in the womb remain a mystery to medicine.
Conclusion
- Calculating the date of birth based on the dates of the last menstruation is convenient and easy - you need to subtract from the last 3 months and add 7 days.
- For many women, the dates calculated by the obstetrician coincide with the actual dates of birth.
- The starting point for the calculation is the first day of the last menstruation, so it is advisable to remember or write down the timing of their appearance.
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No matter how many women give birth, the debate among expectant mothers about how to determine the due date of a child continues for the same amount of time. The difference between your own calculations, ultrasound readings and doctor’s notes is completely confusing. How to determine the due date? Let's try to figure it out, because even in old books about obstetrics there are calculation schemes, and modern medicine should know this all the more.
How to calculate the due date - is there an accurate way?
Modern technologies provide mothers in labor with the opportunity to correctly determine the moment of birth of the baby in several ways:
- Obstetric, which is calculated based on the last menstruation.
- According to the primary movement of the fetus.
- After visiting a gynecologist, who sets the date based on the examination.
- Embryonic, which is determined by the date of ovulation.
- Based on the results of an ultrasound examination.
In addition to the above methods, women in labor determine the required timing using a special online calculator. With so many different ways to determine pregnancy, doctors calculate with accuracy the baby’s birthday, according to statistics, only in 4 cases out of 100, because the duration of gestation is influenced by many different factors, and heredity in the first place.
The community of obstetricians recognizes pregnancy as full not only at 40 weeks, but also at 38, so the due date always moves forward by a couple of weeks in both directions. An experienced gynecologist sometimes determines the day of birth by the shape of the expectant mother's belly, but this method is only effective immediately before childbirth. Let's consider each option for determining the due date separately.
Determining due date by menstruation
This is an old method of calculation, but it is only suitable for those women who have a regular cycle. If your period sometimes comes late or early, there will be large discrepancies in the calculations. The easiest way to determine how much time has passed since conception. Do you remember how many days have passed since the first day of your period? The total number of days counted will indicate the gestation of the fetus.
The term is determined much more accurately using the Keller formula. If you add 280 days to the first day of your last menstrual period, you will get the baby's approximate birthday. Where did the number 280 come from? The average number of the sum of the life expectancy of the fetus and the period that passes before ovulation is taken. The average includes the following indicators:
- the period from the conception of a child to his birth (266 days);
- average menstrual cycle (28 days);
- ovulation date (day 14 of the menstrual cycle).
The obstetric period is equal to the average duration of the menstrual cycle, therefore, when calculating, gynecologists are guided by the indicators of the obstetric calendar and 280 days. The lifespan of a sperm is several days, so even if the time of sexual intercourse is known, it is impossible to determine exactly when ovulation occurred. A baby is considered full-term if born between 38 and 42 weeks, so the error of this method is also two weeks. Using a special table shown in the photo below, the obstetric gestational age is determined.
Calculation of due date by date of conception
Determining the moment of birth by the day of ovulation or the date of conception is very simple. The body of a healthy woman is able to conceive a child only on certain days of ovulation, when the egg has matured and left the ovary. If the menstrual cycle lasts 28 days, then ovulation occurs exactly in the middle of the cycle. Many women say that they feel the moment of ovulation, so it is easy for them to predict the date of birth: at this moment, bloody, not profuse vaginal discharge begins, sexual desire intensifies and a heaviness is felt in the lower abdomen.
How to determine the exact due date if you know the day of ovulation? To do this, add 280 days to the middle of the menstrual cycle. In the same way, the due date is determined by the day of sexual intercourse, if it was a single one. But there is a high probability of inaccuracy here, since sperm live for several days. So, if sexual intercourse took place on the 14th day of the cycle, then conception occurred on the 16th or 17th day.
Determining the due date by the first fetal movement
This method has existed for many centuries, but this does not prevent it from being in demand. And if only a few modern women in labor determine the due date in this way, then when there was no diagnostic equipment, all women used it. The first movement of the fetus usually marks exactly the middle of pregnancy, so the due date is counted from this date. But experienced obstetricians doubt the accuracy of this method, and they have several reasons for this:
- A thin girl leading a sedentary lifestyle feels fetal movement much earlier than planned.
- Primipara women usually feel the first tremors a couple of weeks later than those who give birth again.
- In fact, the baby in the womb begins to move already at the 12th week of pregnancy, but mothers do not feel this yet.
For these reasons, the method of determining a child’s birthday by the first movement cannot be called accurate. The error is especially large if the fetus matures for 41 or 42 weeks, which is considered quite normal. To prevent the doctor and mother from making the wrong decision regarding the fetus, there are more accurate ways to determine the gestational age, for example, ultrasound examination.
How to find out your due date using ultrasound
Even an experienced specialist will not tell the expectant mother the 100% exact date of birth of the child. At best, the due date is indicated with an accuracy of several days, because to a greater extent it depends on the woman in labor: her emotional state throughout the pregnancy and physical health. As statistics show, the method of ultrasound examination is particularly popular today. Greater accuracy of the examination is achieved from 6 to 12 weeks. At later stages, ultrasound is also ineffective as at earlier stages.
In the later stages, even with the help of an ultrasound, it is impossible to determine the exact day of birth of the child. After all, everything is individual: some babies are born weighing 5 kg, others weigh a little more than 2 kg at birth. Also, research in the field of obstetrics and gynecology shows that small women often give birth to large children and, conversely, large women in labor give birth to children up to 2 kg.
The specialist determines the age of the fetus by the size of its head and limbs, and based on the size of the mother’s abdominal cavity, the exact size of the embryo, the condition and size of the uterus, the doctor calculates the approximate moment of birth in any month of pregnancy. In any case, both doctors and expectant mothers believe the results of ultrasound examinations first and foremost.
Table for determining due date
There is another effective way to determine the approximate date of birth - by weight gain. Over the entire period of pregnancy, the expectant mother gains on average from 9 to 14 kg. If twins are expected, then the weight gained reaches 21 kg. In the first trimester, the weight practically does not change, in the second, about 1 kg per month is gained, and already in the third trimester, the woman gains weight rapidly - up to 500 g in one week.
Guided by a special table for determining the timing of childbirth, you can compare the readings of the numbers by weight during weighing. Obstetricians begin to use this table from the 7th month of pregnancy, when the expectant mother is actively gaining weight. According to this scale, a woman should gain about 20 g per week per 10 cm of height. Based on the total body mass index, female figures are divided into the following types in the table:
- Thin – up to 19.8 (group 1)
- Average build – from 19.8 to 26 (group 2)
- Obese - from 26 (group 3)
As soon as you find out that you are pregnant, you are filled with incredible joy. At first, you walk around and just give everyone your happiness. Over time, when the period gets a little longer and the first euphoria wears off, you can’t wait to find out when your baby will be born. You want to plan your birth by at least knowing approximately when the day will come so you can be prepared for anything. Today we will tell you how to calculate your due date.
Pregnancy is always a joy
Due date calculator
Calculation of due date
How to calculate the due date based on the date of conception?
To be completely honest, everyone wants to know their due date. There are two ways:
How else can you calculate your due date?
There is another method that is popular with doctors. With this method, calculating the due date is not as difficult as many people think. Initially, you need to decide what kind of cycle you have. After this, you should remember the last time you had your period. The calculation should be based on when your last period was. In medicine, the first day of menstruation will already be considered as the possible birthday of your child. The estimated date will be calculated from weeks, which are also called medical weeks of pregnancy. What is the difference?
Everything is very simple. If in ordinary life we are accustomed to the fact that pregnancy lasts exactly 9 months, that is, approximately 36 weeks, then according to medical standards this period is 4 weeks longer. In simple terms, the pregnancy will last 40 weeks. The expected date of birth is calculated from the critical days plus 40 weeks. Calculating all this is quite simple. You shouldn't get confused.
The estimated date of birth determined in this way is considered not entirely reliable, and doctors do not rely on it.
You just need to know your cycle and know when the last day of your period is. The preliminary date of birth is calculated very easily. There is a special calculator that will help make the calculation quick. Of course, it is impossible to calculate the sex of a child using this method.
There is also a table for determining the due date. You can also find it on the Internet. In addition to such tables, you can usually find tables for determining the sex of the child. They are usually also based on personal data (menstruation, ovulation). A special calculator will help you quickly calculate your cycle, and you will find out approximately when your baby will be born.
The easiest way to figure out when your baby is due is to go for a routine ultrasound. It is believed that this is the most reliable method. There, the calculation takes place based on the stage of fetal development.
Many women, when they find out about their pregnancy, begin to experience a variety of feelings - some are overwhelmed with joy, others feel confused. And, of course, every expectant mother has many questions. They are especially interested in the day their child is born.
Calculation by date of conception
It has been established that conception is possible only during ovulation, when a mature egg leaves the follicle to meet a sperm. Ovulation usually occurs on day 14 of the menstrual cycle (the period starting on the first day of your period and ending with the first day of your next period). The duration of the menstrual cycle is different for each woman. It can be 28-35 days. On average it lasts 28-29 days.
A woman planning a pregnancy or monitoring her cycle can accurately determine the day of ovulation. In addition, during this period, characteristic signs appear.
It is worth noting that the day of sexual intercourse may not coincide with the day of conception, since the viability of individual sperm in a woman’s body reaches up to 3 days.
So, knowing the day of ovulation, you can quite accurately calculate the date of birth. You just need to add 280 days to this day (the average length of pregnancy). Please note that in this way, only a woman with a regular menstrual cycle can calculate the period of birth of a baby.
We offer an online calculator that will help determine the period of birth of a child:
Calculate due date using menstruation
This method is usually used by gynecologists; it is called obstetric term. When registering, the doctor will definitely ask the woman when she had her last menstruation. And, to calculate the day of birth, he will use the formula invented by the German obstetrician F. K. Negele: from the 1st day of the onset of the last menstruation, 3 calendar months are subtracted and 7 days are added. It is important to note that if the menstrual cycle is not 28 days, then this method of calculation is rather oriented.
Online calculator
(calculation will take a few seconds)
Date of birth according to ultrasound
The most accurate way to determine the time of birth of a child is ultrasound diagnostics (ultrasound examination), but it can only be used in the early stages of pregnancy (up to 12 weeks). Thanks to ultrasound, it is possible to determine the gestational age with high accuracy, and thereby calculate the due date. In the second trimester, the gestational age is determined according to the size of the head and limbs of the fetus, but since each child develops individually, the error in calculations can be up to 7 days. In the third trimester, it is generally impossible to calculate the due date using ultrasound.
Date Based on fetal movements
This method is not accurate. The error may be up to 2 weeks. But still, the expectant mother will have an idea when her baby will be born. So, a woman can feel the first movement of the fetus during her first pregnancy at 20 weeks, and during the second at 18 weeks. It is known that it lasts 40 weeks. It turns out that in order to find out the approximate date of birth you need to add 20 weeks or 22 weeks to the date of the first movement.
Using all these methods, it is unfortunately impossible to calculate a child’s birthday. Many factors can influence this. These include various diseases (polyhydramnios, diabetes mellitus, gestosis, multiple pregnancies, genetic characteristics, irregular menstrual cycle and others). According to statistics, only 10% of babies are born within the period set by the doctor when registering. Therefore, it is impossible to accurately calculate the date of birth, you can only approximately find out when the baby will be born.
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The gestational circle is a convenient and simple tool for determining the gestational age, expected date of birth, as well as some other information about pregnancy. Our gestational disc allows you to determine not only the gestational age, due date, but also the height and weight of the fetus, and even the zodiac sign of the future child.
Our gestational circle is very easy to use.
If you don't know your pregnancy date, scroll through the inner circle so that the green arrow points to the first day of your last period.
green arrow
Wherein “today” arrow will indicate today's date and week of pregnancy, as well as the height and weight of the fetus. Then PDR arrow will indicate the expected date of birth.
"today" arrow
If you already know your due date, then scroll the inner circle so that “today” arrow indicated the week of your pregnancy. Then it will indicate the height and weight of the fetus, and PDR arrow will indicate the expected date of birth. In this case, the green arrow will point to the first day of the last menstruation.
PDR arrow
See also:
The easiest and most accurate pregnancy calculator: how to use the gestational circle
From school biology lessons, everyone knows that it takes a woman 9 months to bear a fetus. However, this is a very average value, which is not used in obstetrics and gynecology. Doctors monitor by week and trimester. But these indicators cannot be called absolutely accurate. The period from the beginning of the last menstruation immediately until childbirth takes an average of 40 weeks or 10 obstetric months. The gestational disc will help you find out your due date at the beginning of your last menstruation and track changes.
What does "gestational" mean?
Many people hear this word for the first time in a antenatal clinic. The Latin gestatio literally translates as “gestation.” Therefore, “gestational” means “relating to pregnancy.”
Gestational age is calculated from the moment of conception. It is extremely difficult to determine exactly when this happened. It may take up to several days after sexual intercourse for a fertilized egg to implant. At the initial stage of embryo development, even a few hours play an important role. Therefore, the inaccuracy in determining the “starting point” leads to a relative arbitrariness of the calculation.
Gestational disc to determine due date
There are different calculators, the main purpose of which is to determine the date of birth of the baby. Gestational circle- an indispensable tool for preparing for childbirth and better monitoring the pregnancy process. With its help, every woman can determine the “date X” at home. This is necessary, since premature and late births pose the same danger. Therefore, it is important to calculate the expected day of birth and carefully monitor the body’s signals as it approaches.
Statistics say that about 2% of babies are born exactly on the calculated day. The date that the calculator shows is best considered conditional. Most likely, the baby will be born a few days earlier or later. Normal birth is considered between 38 and 40 weeks. But each organism has its own unique characteristics. Some women reach 42 weeks, in which case maximum attention from doctors is required.
Gestational circle is one of the most informative calculators. In addition to the approximate date of birth, it can be used to determine the height and weight of the embryo as it develops. In addition, many parents are interested in under what zodiac sign and in what year of the animal according to the eastern calendar the child will be born. This helps some couples choose a name.
How does the gestational circle work?
Using this visual calculator, it is easy to determine the due date and monitor the height and weight of the fetus during pregnancy. The external drive is divided into 12 months. Each day corresponds to one division on the scale. For convenience, long marks indicate every 5 days.
The numbers 1-40 on the moving part of the disc correspond to the weeks of pregnancy. Also, using a background with different saturation, trimesters are highlighted: the first - from to , the second - from to , the third - from to . Closer to the center is the weight scale, and at the last level is the fetal growth scale.
There are 3 arrows on the circle: green tonka (the first day of the last menstruation), EDP (estimated date of birth) and a static “today”. The center of the circle displays basic information: the beginning of the last menstruation, the expected date of birth and the child's zodiac sign. In the area under the disk, the number of weeks and days before giving birth, as well as zodiac characteristics, are instantly calculated.
How to use a gestational disc to determine your gestational age
The gestational circle is used by many obstetricians and gynecologists in different countries, including Russia. The simplicity of the method allows it to be used by absolutely every woman.
When planning a pregnancy, it is especially important to keep a menstrual calendar. This will help determine the expected date of birth as accurately as possible. To calculate the gestational age by gestational circle, simply move the thin green arrow to the date of the start of your last menstrual period. The PDP arrow will indicate the date of birth, provided that the pregnancy ends at 40 weeks. Using the “today” arrow, it is easy to track the average growth and weight of the fetus each week.
For example, the last menstruation was from December 12 to 16. For calculations based on the gestational circle, only the first date is important - December 12. Set the thin green arrow to this number. When twisting the arrow, pay attention to the center of the circle. This is much more convenient than peering at the divisions. The “today” arrow indicates that the woman is at the beginning of the 8th week of pregnancy, the fetus has grown to 18 mm and weighs 1 g. You need to prepare for childbirth within 1-2 weeks of September 18.
What should a woman do who does not know the date of her last menstrual period?
In this case, the gestational circle will be ineffective for independently determining the date of birth of the child. Doctors usually prescribe a blood test for hCG. Human chorionic gonadotropin is a hormone that is released in a woman’s body after implantation of the embryo in the uterus at 4 obstetric weeks. It is from this moment that you can get the most reliable results.
When using the strip test at home, the second strip may be translucent. This indicates either that the test is unsuitable or that there is a small amount of the hCG hormone in the body. To get reliable results, you need to try again after a week if menstruation does not start. A faint second stripe may appear in women taking hormonal medications, regardless of pregnancy.
A home test only shows the presence of pregnancy. Based on the results of a biochemical blood test, its duration is determined. Don't put off checking. The hCG test is most reliable in the first 12 weeks. The hormone level gradually decreases, and at later stages it is difficult to determine the time of conception.
Once the week of pregnancy is known, the gestational circle can be used to calculate the due date and determine the size of the fetus. To do this, just set the “today” arrow to the mark corresponding to the current date.
For example, it's week 9. At this stage of development, the embryo has reached 23 mm and weighs 2 g. The expected date of birth is September 9. The green arrow indicates the approximate date of the start of the last menstruation.
Errors
Bearing a fetus is a complex process that occurs differently for every woman. Moreover, the course of the first pregnancy does not mean that subsequent ones will follow the same scenario.
The pregnancy calculator allows for some error. In addition, errors cannot be ruled out when setting up the source data. The accuracy of the calculation depends on the individual characteristics of the organism. The pregnancy wheel shows the most accurate result for a standard menstrual cycle of 28 days. If the duration is longer, for example, 35 days, then ovulation will occur on average on the 21st day. This leads to an increase in the difference between obstetric and embryonic periods.
In addition, the error may be caused by inaccuracy in determining the embryonic period. The sperm can survive in the female body for up to 3 days. Fertilization can occur at any time. Taking into account all factors, including the individual characteristics of the expectant mother’s body, the error in calculating the expected date of birth often reaches 2 weeks. Ultrasound gives more accurate results, although the method of calculation based on the beginning of the last menstruation is recognized throughout the world as one of the best.
Why in the first two weeks the height and weight on the disk correspond to zero
You can notice that in the first two weeks the indicators are zero. However, this period is part of the entire pregnancy cycle. The fetus develops surprisingly quickly in the womb. Therefore, in determining the date of birth, every day is important. At the same time, there are different periods - obstetric and embryonic, which are important not to be confused.
Some people mistakenly believe that the first week is counted from the moment of conception. In fact, pregnancy begins on the last day of the menstrual cycle. Directly during this period, the birth of a new life might not have occurred. The moment of conception depends on ovulation and varies within a couple of weeks.
With a standard menstrual cycle lasting 28 days, ovulation occurs on the 14th day. In this case, the embryonic period will lag behind the obstetric period by about 2 weeks. In practice, this means that at the end of the first month of pregnancy, the actual age of the embryo is only 2 weeks.
Why sometimes calculations by different methods do not match
Many women are surprised to find that their due dates according to different calculations do not coincide. Which one should you believe?
In official medicine, it is believed that during the first trimester, embryos develop equally. On ultrasound, the gestational age is determined using a table that corresponds to the size of the fetus for a certain period of development. For example, a calculation based on the last menstruation shows a result of 12 weeks, but the diagnostician calls it 11 weeks. The deadline set during the first ultrasound is considered more reliable. In the example given, the difference is due to early ovulation, but it can also be late. For the doctor, the result of the ultrasound examination is a priority.
During the second and third trimesters, each fetus develops at its own pace. Therefore, data from average tables may not fully correspond to reality. Deviations within one week are considered normal. In the ultrasound protocol, the specialist indicates the period of fetal development.
The gestational circle gives an idea of how the unborn baby is developing every day. At the beginning of the first trimester, the embryo gains only a couple of grams every week, but the difference, for example, between and 21 weeks is on average 71 g. Every woman is interested in learning how the fetus changes. With the gestational circle, observing becomes simple and even more fun.
The most important weeks of pregnancy
In order for the fetus to develop correctly and the child to be born healthy, the fact of pregnancy must be established as early as possible. It is not at all necessary that the expectant mother will intuitively sense conception, or that obvious signs will appear in the first weeks in the form of a heightened sense of smell, morning sickness, etc. There are often cases when a woman learns about pregnancy only by an enlarged belly.
The following factors pose a particular danger to pregnant women:
- Unhealthy habits.
- Stress.
- Unbalanced diet, deficiency of nutrients (mainly iron and folic acid).
- Great physical activity.
- Overheating or hypothermia.
- Taking medications that are incompatible with pregnancy.
- Infectious and inflammatory diseases.
It is necessary to prepare the body for pregnancy in advance to minimize risks for the fetus and the expectant mother. But even if everything goes according to plan, there are times when you need to be extra careful. If at any stage of pregnancy a woman feels severe discomfort, burning or even unreasonable anxiety, she should visit a doctor.
When to take extra care
Critical periods coincide with the phases of active enlargement of the embryo and placenta. The most dangerous weeks are the following:
- I trimester - 2-3, 4-7, 8-12.
- II trimester - 18-22.
- III trimester - 28-32.
The tricky thing about the first weeks is that a woman may not be aware of pregnancy. As a result, the required conditions are not met. From 4 weeks the main organs are formed. During this period, it is especially important to follow the doctor’s instructions in order to prevent pathologies. At the last critical stage of the first trimester, the placenta is formed - a natural shield that will grow with the fetus.
The period from week 22 is considered the most important. At this time, the unborn baby is most active. The greatest risks to the life of the fetus and the health of the woman are sexually transmitted infections. One of the main conditions is to use barrier protection during sexual intercourse.
By the beginning of the third trimester, the fetus is most similar to a baby, but it is not yet able to survive separately from the mother’s body. The causes of premature birth may lie in placental abruption, infections and isthmic-cervical insufficiency. To prevent this, you need to follow absolutely all the doctor’s instructions, take care of your own health and eliminate stress.
There are no critical periods in the gestational cycle. This is because they don't have to be difficult at all. The more you focus on the dangers, the greater the destructive effects of stress. You can use the pregnancy wheel throughout the entire pregnancy period. The diagram is convenient for tracking the transition to a new trimester, the stages passed and the approaching date of birth.
Description
The universal pregnancy calculator is a convenient and practical tool for calculating a number of parameters that are important and interesting for the expectant mother. The calculator is a circle similar to a watch dial, the inside of which can be rotated to set one or another hand to the desired position. For example, by setting the thin green arrow so that it points to the first day of the last menstruation, you will use the “PDR” arrow to determine the date of future birth, and by using the “today” arrow you will find out what week of pregnancy you are now, and what the height and weight of the fetus is. present day. The Pregnancy Wheel can be used in other ways. For example, if the birth has already taken place, then you can set the “Estimated date of birth” arrow so that it points to the day of birth. Then a thin green arrow will show you the date on which you had your last menstrual period before becoming pregnant. Among other things, the calculator determines the zodiac sign of the unborn child, and even his zodiac animal according to the eastern calendar.