1 week of pregnancy after conception: Calendar and obstetric calculation methods


1 week of pregnancy after conception: calendar and obstetric methods of calculation

  • Distinctions from embryonic age
  • Behavioural term at ultrasound
  • Definition

Finding the long-awaited two stripes, the woman realizes that very soon she will have a baby, and possibly two.

When she comes to see an obstetrician-gynecologist, she is interested in the timing of the pregnancy. Very often, after hearing the number in the weeks, the expectant mother is embarrassed and thinks that the doctor thought something was wrong, because sexual intimacy was at a different time (usually 2 weeks later).

Don't worry, the doctor told you the obstetric term of pregnancy, and you, assuming that when the conception occurred, counted embryonic. Both are true.

However, all over the world it has been customary for obstetricians and gynaecologists to determine the duration of pregnancy since the first day of the last menstruation – the so-called obstetric period. There are several reasons:

  • First, this method has existed for a long time, even since they did not know about ovulation, there were no ultrasound diagnostic devices, and the main sign of pregnancy was the absence of menstruation.
  • But second, each woman has its own length of menstrual cycle. Somebody has 21 days, somebody can reach 35. Also, some women do not have a regular cycle. Therefore, in order not to calculate the day of ovulation in each case, it is easier to navigate by the date of the beginning of the period.
  • Three, not every woman knows exactly when the fertilization occurred. And even if she remembers the day of sexual intimacy on which it is likely to have occurred, the ovum and sperm can be found a few days later.
  • B-fourth, for an accurate statement of the gestational age are still guided by other data: the results of the first trimester ultrasound, the date of fetal movement, the size of the uterus.

What is the difference between an obstetric term and an embryonic term

informationAs already mentioned, an obstetric term is defined by month and an embryonic term by date of conception.

In a regular 28-day menstrual cycle, the first one is on average 14 days larger than the second one, because ovulation occurs in the middle of the cycle (during which time conception takes place).

However, if a woman has an irregular menstrual cycle, the difference can be more than a month.

Example, if a woman ovulates for 53 days, the difference is 53 days. This is possible with polycystic ovarian syndrome, hormonal disorders, stress, and some medications.

Also, there are cases where a woman had her last period before her previous pregnancy. Then she was breastfeeding, and at that time there was lactation amenorrhoea (no menstruation).

With a decrease in the amount of feeding she began to mature the egg, and then when she met the sperm during the ovulation period she became pregnant.

In this case, we can't talk about the term as such, because menstruation was more than a year ago!

Midwife in ultrasound

Ultrasound is one way to determine the midwife's gestational age. In some cases, it is the main indicator (e.g. in the case of pregnancy with lactation amenorrhoea or irregular menstruation).

In the first trimester, the main indicator for the duration of pregnancy is CTR (coccyx-parietal size) and the size of the fetal egg. The doctor compares these figures with the averages and gives an opinion on the timing. During this period, babies are the least different in size from each other. At the following ultrasounds, the circumference of the abdomen and the fetal head, the length of the hip, are evaluated.

But in later terms, all babies, like us, differ from each other: someone taller, someone slightly larger, someone with slightly longer legs … Therefore, when comparing the results with the average there is a large error due to the physiological characteristics of each child.

Also here can make their own corrections and violations of fetal development (hypotrophy, hypoxia, hemolytic disease, fetoplacental insufficiency).

AdvancedThe ultrasound-scanning gestation period is almost the same as that of a normally developing pregnancy, as the average size tables have already been supplemented with the 2 weeks from the time of the period until conception. Only if the ultrasound is performed at the very beginning (up to 4-6 weeks), the set period can coincide with the embryonic one.

Based on the above, the most accurate pregnancy term is the one that is set before 12 weeks of pregnancy.

How to determine the gestational age of the midwife

Midwife's gestational age is calculated over weeks from the first day of the last menstruation. The gynaecologist determines the expected date of birth and issues a certificate of incapacity for work for pregnancy and childbirth. To calculate your baby's birthday, you can use the following formulas:

  1. Last day of menstruation – 3 months + 7 days. For example, the woman's last menstruation was on September 13th. From this date it is necessary to take three months (it will turn out on June 13) and add 7 days. Date of expected delivery June 19,
  2. Last day of the month + 9 months + 7 days. For example, September 13 + 9 months (June 13)+7 days (turns out June 19).
  3. A more complicated way to add 280 days to the last day of menstruation.

And finally, it is worth noting that whatever method is used to determine the duration of pregnancy and childbirth, nature gives us a run in 4 weeks, because the birth in time are those that occurred from 38 to 42 weeks of pregnancy. Yes, and the baby knows better when to be born.

Source: https://baby-calendar.ru/mama/opredelenie-sroka-beremennosti/akusherskiy-srok/

Why do obstetric gestation and the actual gestational age differ

1 week of pregnancy after conception: calendar and obstetric methods of calculation

Most women who are expecting a firstborn baby do not know what the obstetrical term of pregnancy is and what the real term is. When setting the gestational age, doctors start from the date of the beginning of the last period before the pregnancy. This is how they calculate the midwifery period. It differs from the embryonic (real time).

Real time coincides with the date of ovulation in the same monthly cycle. With a menstrual cycle of 28 days, it is considered that conception occurs on day 14 (the day of ovulation). Often the difference between these two counts is two or sometimes three weeks.

To calculate the time of conception as accurately as possible, it is important for doctors to know when the last menstruation before pregnancy began.

From this point on, the midwifery period is counted and the duration of the pregnancy is set.

Usually women have a 28-day menstrual cycle, so the best time to conceive a baby is the 14th day after the start of the “critical days”, i.e. when ovulation occurs.

The difference between the two counts is about two weeks, so when you determine the provisional date of birth, it is allowed to deviate from the set period by two weeks (two weeks before and two weeks after the provisional date of birth).

For example, if 5 weeks have elapsed since the beginning of your period, then using this calculator, the doctor will give you the fifth week of pregnancy. And from the moment of conception, three weeks will pass and the embryo will actually be in its third week of development (Fig. 1). But these are only average data and calculations, which are carried out approximately.

Each woman's body is specific, and generally accepted medical indicators may differ from the individual timing.

According to the statistics, half of the women are fertilized in the same way as the doctors calculated, that is, 14 days after the beginning of menstruation.

Other women are fertilized earlier.

The main difference between gestational age and the actual gestational age is that the first one is oriented to the date of the first day of the last period, and the second one is equal to the date of conception.

Picture 1: Embryo and fetus development.

So how is there a significant difference between the two methods of calculation, the question arises: why do we need an obstetric term if we can calculate the real one? This is the problem.

To determine the embryonic duration of fertilization of the egg, there are obstacles. Future mothers had to calculate the timing of foetal delivery at the time of the absence of ultrasound or tests, and there was no evidence of ovulation.

The only indicators were bleeding or lack of bleeding.

Monthly cycle is individual for each woman, and it is not possible to determine the exact date of possible ovulation. Not every woman remembers the exact date of sexual intercourse and possible fertilization. In addition, conception could have happened a few days later than expected.

Therefore, doctors calculate the midwifery period and use it to set the weeks of pregnancy, assign all the tests and examinations of future mothers. This interval is also the date of future births.

How to calculate the period of conception by yourself

Any future mommy is able to calculate it without her doctor's help. It's enough to know the date of the latest bleeding secretions and the duration of your cycle. Then the time from the date of your period to the day you become aware of your situation is calculated.

The duration of the cycle should be taken into account, because if it is longer than 28 days, fertilization may occur later. If you have forgotten the date of your last menstruation, an accurate analysis of human chorionic gonadotropin can help.

It can give you an approximate age of the fetus.

To determine the actual date of sexual intercourse or fertilization, you should know the exact day of sexual intercourse or fertilization.

This is what modern electronic tests can do to help you do so, and with the help of electronic sensors it is possible to determine the date of conception and the estimated gestational age.

Much easier to calculate if you remember the date of the last sexual intercourse. Then you just need to count the days that have elapsed since then and translate them into weeks of pregnancy.

Medical timing methods

Medical methods for calculating timing

Medicine currently uses a variety of methods to accurately determine the timing of conception. These are the following methods:

  1. Fetal ultrasound. This method has been used for a long time in gestation diagnostics. The most precise term is determined at an early examination – up to 8 weeks. Since a healthy embryo develops during this period, it is possible to set the exact gestational age (up to 24 hours) according to the size of the embryo. After a while, the individual development of each fetus begins, which can show the method of ultrasound examination. Any deviations can be noticed on the screen, and the doctor, knowing the norm of development, makes the appropriate diagnosis. For example, the fetal body length or head size may be an anomaly. In such a case, a deviation from the norm is allowed within a week or ten days. If the difference between fetal development and normal development is two weeks or more, the doctor may diagnose a delay in intrauterine development. Then the attending physician gives recommendations on nutrition, recommends a healthy lifestyle.
  2. The measurement of rectal temperature. This method is based on the daily measurement of the lying temperature by inserting a thermometer into the anus. On normal days it hardly reaches 37C, but during the time when ovulation occurs, it rises to 37.3C. The day of fertilization may not coincide with the day of sexual intimacy. The sperm can live in a woman's body for another three days, waiting for the egg to appear. If sexual intercourse occurs a few days before ovulation, fertilization may occur a couple of days after contact. Therefore, according to experts, this method of determining the real term is not entirely accurate.
  3. Abstetric method of determining. It comes from the date of the last menstruation. The inaccuracy ranges from a week to two. Calculated according to the formula – 10 monthly cycles are added to the date of menstruation before pregnancy, i.e. 280 days on average (28˟10). Or, if the exact date of ovulation is known (12-16 days of the cycle), they add 264 days.
  4. Consultation and examination by a gynecologist. At the beginning of pregnancy, the doctor cannot yet determine the uterine size and position of the fetus. This method is effective in the second and third trimester.
  5. Blood analysis on hCG. This method primarily helps to identify possible complications of fetal development at an early stage. Serious abnormalities are a signal of an abnormal development, a frozen or ectopic pregnancy.
  6. First movement. According to the doctors, the baby gives the first signs of his presence in the tummy of his mother in an average of 20 weeks. This is also a method of determining the timing of pregnancy. The first movement is especially felt in the horizontal position when the baby is uncomfortable and tries to turn around.
  7. Uternate size. At the beginning of the second trimester, the doctor begins to measure the size of the uterus. There are norms and tables here, according to which the doctor can set the exact period of pregnancy.
  8. Heartbeat of the fetus. First, it is determined only by an ultrasound scan, then the doctor listens to it with a special tube (obstetric stethoscope). These measurements determine the position of the fetus, placenta.


Which conclusion can be drawn from this

May be inferred from this – it is almost impossible to determine the exact date of conception and delivery to the day of conception.

But a woman will be able to distinguish between the concepts of obstetric and the actual term of pregnancy, knowing their characteristics, and will not be surprised that the term set by the doctor does not coincide with her own calculations based on the actual date of conception.


Whichever way the future mommy tries to calculate the timing of the long-awaited crumbs, the baby will choose its own date when it wants to be born, and any calculations may turn out to be wrong.

Source: https://vseproberemennost.ru/raznoe/akusherskij-srok-beremennosti-i-realnyj.html

1 week of pregnancy: description, feelings, development of the fetus

1 week of pregnancy after conception: calendar and obstetric methods of calculation

Pregnancy is not counted in months, for the convenience of gynecologists the obstetric method of calculating the period of child-bearing by weeks is followed. The first week is the most mysterious week ahead. It is calculated theoretically by a gynecologist based on the first days of the cycle and the estimated day of ovulation.

Medicine counts from the first day for the last menstruation. This is due to the fact that it is difficult to determine the exact day of conception – each woman's ovulation occurs on different days of the cycle, depending on its duration and the physiological characteristics of the future mother. For this reason, gynaecologists are always guided by the term of obstetrics rather than embryonic.

Normal pregnancy lasts 40 weeks, 280 days or 10 lunar months.

From a scientific point of view, in the first week of pregnancy a follicle ripens – a liquid-filled vial in which the ovum is located. After leaving the shell, she lives between 24 and 48 hours. The inner layer of the follicle walls produces hormones of estrogen, which contribute to the recovery and growth of the mucous layer in the uterus, preparing its cavity for the upcoming pregnancy.

You are wondering what rules to follow on each week of pregnancy?

We invite you to read the detailed pregnancy calendar on our website, which details what happens to the formation of the fetus at each of the 42 weeks – a link.

At the time the egg will fertilize the sperm. Once the cells have merged, they will begin to divide and the zygote from the fallopian tube will enter the uterine cavity. It's a special cell that stores the genetic material of the father and mother. The future child will acquire genetic characteristics from both parents.

Implantation takes place within 7 days. In the uterus, the zygote will be attached to the wall and in the new house it will develop further, gradually becoming a little man.

The embryonic period is the most important. The woman is not yet aware of the onset of pregnancy, and the embryo undergoes successive stages of development. At this time, one or more fetuses will develop in the uterus and a chorion will be formed that participates in the formation of the placenta.

1 week of pregnancy coincides with the beginning of the menstrual cycle. The uterine muscles shrink, expelling the expelled layer of endometrium, and the woman's health improves.

At this point in time, the woman knows nothing about her “interesting” position. Accordingly, all symptoms and signs are absent yet – mammary glands do not swell, there is no toxicity, fatigue and intolerance to odors. During this period, the vaginal discharge pattern changes slightly, which is considered the norm.

Do not determine pregnancy by passing blood to hCG level. The test will also not show any changes – if the body is healthy and there are no hormonal failures, it will have only one stripe.

There are a number of symptoms that women rarely experience in 1 week:

  • mucous excretions with thin blood streaks as evidence of embryo attachment;
  • stretch and pubic pressure;
  • negative smoking and alcohol – a protective reaction of the body at the subconscious level;
  • emotional instability.

In the first week of pregnancy, fatigue increases. A woman gets tired faster and can't handle normal physical activity. It's as if the body is in a “sensitive mode” and trying to maintain its strength.

The same symptoms are not seen in all expectant mothers, but can only be noticed if one listens to one's own body at all times.

In spite of all the advances in modern medicine, it's impossible to confirm 1 week of pregnancy. All we have to do is wait for the signs to show up. No gynecologist will be able to detect the onset of pregnancy in the first week.

Mother's 1 week of pregnancy changes

Female body begins a global restructuring right after conception, trying to provide for itself and the embryo.

  1. The release of large quantities of estrogen can have an impact on the breast. They increase in size, the nipple halos get darker and swell. The breast becomes painful.
  2. The central nervous system changes. The influence of the vagus nerve increases and the mother-to-be becomes inattentive, absent-minded, the taste perception changes, salivation increases. Weakness and dizziness are a frequent companion.
  3. Beginning to rebuild the circulatory system: uterine blood flow increases, the volume of circulating blood increases. A woman's body tries to adjust to the ability to supply sufficient oxygen to the fetus.
  4. The basal temperature changes and if this method of ovulation control is used in planning, the expectant mother learns about the onset of pregnancy at the earliest possible time.

Nausea and vomiting appear much later. If you have toxicosis attacks in the morning or in the evening, you may have a slightly longer period of time than you think.

What happens to the fetus in the first week of pregnancy

The fusion of an egg that has emerged from the follicle with a sperm symbolizes the birth of a new life. This is just one cell that has to go through a huge path of development in the womb.

From the moment of fertilization in the zygote there is an active division of cells, which from the unorganized mass form a hollow ball – blastocyst.

While the embryo is now only 0.2 mm in size, the sex of the future child is already determined – it depends on the sexual chromosome given to it by the father X or Y. The rest of the chromosomal set contains data according to which all fetal systems and organs will develop.

The outer layer of blastocyst, penetrating into the uterine walls, begins to synthesize the pregnancy hormone – chorionic gonadotropin. Early pregnancy is measured by hCG levels, which is one of the most reliable indicators.


Menu for a woman planning to become a mother differs from the usual diet. Nutrition should be complete and balanced, rich in proteins and moderate in fat.

The whole diet should be made up of fresh vegetables and fruits in raw form or thermally treated.

Physicians, obstetricians, gynecologists, and nutritionists give some nutritional advice to expectant mothers in their first week of pregnancy.

  1. Review your own nutrition system. Eliminate all harmful products and seek the help of a nutritionist, who will help to create an individual full menu, where all the necessary vitamins and minerals for a future mother will be
  2. The basic diet of a pregnant woman should be lean meat, fish, vegetables and fermented milk products. Meat contains the necessary building protein, fish – unsaturated acids and magnesium. Vegetables have a list of mandatory vitamins, which should get into the mother's body during child-bearing. Fermented milk products help to normalize stools and remove toxins in a timely manner.
  3. Leave fried, salty, spicy foods out of the way to avoid heartburn and gastrointestinal problems. Limit the use of sweet fruit by giving preference to fresh fruit. Drink as little strong tea and coffee as possible
  4. The use of raw fish and seafood is strictly forbidden – they may contain parasites that penetrate the mother's body and take away vital trace elements.

Vitamins and minerals, if not enough in the products, should be taken in separate complexes. This will reduce the risk of malformations in the development of fetuses caused by deficiency of nutrients.

Special attention should be paid to vitamin B9, or folic acid. It can reduce the negative impact of external and hereditary factors on the embryo, favorably influence the formation of the nervous system and the overall condition of the fetus.

Other vitamins will be prescribed by the doctor after examination, tests and registration.

In the first week of pregnancy it is highly discouraged to adhere to strict diets and strict dietary restrictions. If a pregnant woman is overweight, you should seek the help of a qualified dietician. The specialist will make a balanced menu individually, taking into account all the nuances.

Very often during pregnancy a woman starts eating for two. You don't have to do that! Overeating too much will only lead to overweight. Excess kilograms will harm the future child, and the constant weight gain will negatively affect the health of the pregnant woman on the last terms.

Medical and life style advice for the mother-to-be

When considering pregnancy, a woman should think about her lifestyle and adjust it according to the recommendations. Taking care of yourself before conception greatly increases your chances of bearing and giving birth to a healthy child.

  1. Morally prepare for the changes to come. The next 9 months will see unusual processes in your body, most of which are unpleasant. Toxicosis, abdominal pain, changes in body shape, drowsiness and frequent calls to urination are natural processes. Be patient with them, without irritation. After 39 weeks it will all be over and you will have a long-awaited baby in your arms.
  2. Try to have more rest and just sleep. Spend some time sleeping in the afternoon, surround yourself with beautiful things.
  3. Constrain communication with unpleasant people, try to avoid conflicts and stressful situations at work and at home.
  4. Departure yourself from saunas, baths and hot baths.
  5. When you find out you are pregnant, go to a doctor immediately. The specialist will use an examination or ultrasound to confirm that the uterus contains a foetal egg and assess your overall condition. If necessary, the gynaecologist will prescribe maintenance medications and will do everything necessary to maintain pregnancy.
  6. Medicines should be taken with caution, only on prescription. The usual cold should be treated with folk remedies, resorting to pharmacological drugs in the last place. Avoid contact with sick people, do not visit crowded places during epidemics, avoid hypothermia.
  7. Freeze from alcohol, smoking and strong psychotropic drugs.

  8. Extreme sports are not for you anymore – take care of yourself and your future child. A surge of adrenaline won't do you any good.
  9. No X-rays or fluorography.

Danger 1 week of pregnancy

In the first week of pregnancy, spontaneous abortions often occur, miscarriages that the woman does not even know of when she is having another menstruation.

Extra-uterine pregnancy is another danger. It occurs when for some reason the fertilized cell is attached to the fallopian tube or enters the abdominal cavity. This condition threatens the life of the woman and requires prompt intervention. The first ultrasound is prescribed specifically to rule out incorrect attachments.

Chromosomal anomalies are another reason for early self-abortion. The embryo stops developing and the mother's body rejects it.

From hormonal failures, inflammation of the endometrium, scars and bluechiae in the uterus, blastocyst implantation is difficult, the embryo dies and is removed during the next menstruation.

The risk factors include taking strong drugs or antibacterials. This leads to termination of the pregnancy or to severe consequences for the fetus during its subsequent development.

Fetal ultrasounds

Uzi – the first week of pregnancy Uzi – the first week of fetal development in the first week of pregnancy

Fetal development in the first week of pregnancy, conducting an ultrasound scan, you can see a thickened layer of endometrium in the uterus cavity, which is being prepared for the attachment of the fertilized egg.

At the same time, the ovaries are examined in order to determine which one has the dominant follicle. It looks like a rounded dark cavity and is different in size from others

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