Rus Articles Journal

Birthday according to the plan of

the Doctor of a maternity welfare unit observing future mother surely determines the term of pregnancy and designates estimated date of childbirth. Why these data and how they can be recognized are necessary?

Why it is necessary?

Of course, it is necessary to know pregnancy term not for satisfaction of idle curiosity and not to define under what zodiac sign the kid will be born, - these calculations have quite definite purposes.

In - the first, the term of pregnancy is necessary for careful control of pre-natal development of a fruit, to each term there correspond certain standard indicators of growth and development from which deviations can demonstrate emergence of various complications. For example, at discrepancy of the sizes of fetal egg (on early terms) to the estimated term of pregnancy there is a suspicion on not developing pregnancy. On later terms discrepancy of the sizes of a fruit can speak about such pathology of pregnancy as a delay of pre-natal growth of a fruit.

In - the second, needs determination of terms of pregnancy most precisely to determine the estimated date of childbirth (EDC), It is date is important for several reasons.


At last, the exact term of pregnancy is necessary for timely providing prenatal holiday - a leaf of disability on pregnancy and childbirth (the sick-list which is given by the doctor the obstetrician - the gynecologist in 30 weeks of pregnancy).

calculation Methods

For determination of term of pregnancy a number of methods exists. Let`s talk about them in more detail.

Calculation of PDR on time of the last periods. In practice of obstetricians - gynecologists the method of definition of date of the forthcoming childbirth on the first day last before the come pregnancy of periods is widely applied. From this point the uterus already begins to prepare for fertilization, on the place of the torn-away mucous membrane (endometriya) is formed new endometry, ready to accept the impregnated ovum. Approximately in the same terms in an ovary of the woman the ovum which will be impregnated by sperm - tozoid begins to ripen, as will give rise to pregnancy.

to Determine by

the true duration of pregnancy usually can be difficult. It is connected with the fact that it is difficult to establish the exact term of an ovulation (if special methods of diagnostics - the test for an ovulation were not used, ultrasonic monitoring of maturing of a follicle), time of advance of spermatozoa on bodies of reproductive system of the woman, and also exact date of fertilization (if only it was no only sexual contact within a month or procedure of fertilization in a test tube - extracorporal fertilization). In most cases duration of the pregnancy calculated on the first day of the last periods is made by 280 calendar days, 10 obstetric months (40 weeks) or 9 calendar months. However there are data on the birth mature (capable to independent extra uterine life) children at pregnancy, proceeding of 230 - 240 days. Along with it cases of considerable prolongation of pregnancy (so-called perenoshenny pregnancy) meet. In literature there are data when pregnancy continued more than 300 days.

Should tell

that full-term pregnancy is considered already in the term of 38 weeks as in most cases by this time the kid is ready to independent extra uterine life and can quite “ask“ on an exit. By this time at the child all signs of prematurity disappear and there are all indicators inherent in a mature fruit. However in some cases the full-term fruit can have a number of signs of immaturity and vice versa so the concepts “full-term“ and “mature“ a fruit are not identical. Therefore also pregnancy duration in some cases is considered more than 40 weeks as norm.

to determine the estimated term of childbirth on the first day of the last periods, it is necessary to add by this day 280 days. To facilitate calculation, it is possible to count of date of the first day of the last periods 3 months back and to add 7 days. For example, if the first day of the last periods was on June 23, then, having counted 3 months back (on May 23, on April 23, on March 23) and having added 7 days, you receive estimated date of childbirth - on March 30.

of Kopchiko`s
pregnancy Term (in weeks and days) - the parietal size (cm)
of 2 N 0,3
of 3 N, 2 0,4
of 4 N, 3 0,5
of 4 N, 4 0,6
of 4 N, 5 0,7
of 4 N, 6 0,8
of 5 N 0,9
of 5 N, 2 1
of 5 N, 3 1,1
of 5 N, 5 1,2
of 5 N. 6 1,3
of 6 N, 1 1,4
of 6 N, 2 1,5
of 6 N, 3 1,6
of 6 N, 4 1,7
of 6 N, 5 1,8
of 6 N, 6 1,9
of 7 N 2
of 7 N, 1 2,1
of 7 N, 2 2,2
of 7 N, 3 2,3
of 7 N, 4 2,4
of 7 N, 5 2,5
of 7 N, 6 2,6
of 8 N 2,7
of 8 N, 1 2,9
of 8 N. 2 3
of 8 N, 3 3,1
of 8 N, 4 3,3
of 8 N, 5 3,4
of 8 N, 6 3,5
of 9 N 3,6
of 9 N, 1 3,8
of 9 N, 2 3,9
of 9 N, 3D. 4,1
of 9 N, 4 4,2
of 9 N, 5 4,4
of 9 N, 6 4,5
of 10 N 4,7
of 10 N, 1 4,9
of 10 N, 2 5,1
of 10 N, 3 5,2
of 10 N. 4 5,3
of 10 N, 5 5,5
of 10 N, 6 5,8
of 11 N 6
of 11 N, 1 6,1
11 of N, 2 6,3
11 of N, 3 6,5
11 of N, 4 6,7
11 of N, 5 6,9
11 of N, 6 7,1
of 12 N 7,3
of 12 N, 1 7,5
of 12 N, 2 7,7
of 12 N, 3 7,9
of 12 N, 4 8,1
12 of N, 5. 8,3
of 12 N, 6 8,5
of 13 N 8,6

Calculation of PDR on an ovulation. One more method of definition of the estimated date of childbirth (EDC) is its calculation on an ovulation (to ovum exit time from an ovary). The method consists in the following: of the first day of the expected, but not come periods it is necessary to count back 14 - 16 days and to the received date to add 273 - 274 days. However the accuracy of this method depends on several factors.

In - the first, the method suits only those women whose cycle was regular and made of 28 - 30 days. Only in this case can be assumed that the ovulation took place on 14 - 16 - y day of a menstrual cycle.

In - the second, fertilization not always comes in day of an ovulation. In other words, happens so that the ovulation occurred, and sexual contact took place only after a while. The matter is that ability of an ovum to fertilization averages 24 hours, however the question of survival of spermatozoa in a genital tract of the woman is essential. In literature there are data that viability of spermatozoa keeps - sya 2 - 3 days, and according to some information - to 7 days.

First stir of the kid. And, as a rule, each woman remembers this important event for any future mother that day when her kid “has for the first time an effect“. And for the doctor conducting pregnancy, this day is one more reference point in definition of PDR. To date of the first stir add 5 obstetric months (20 weeks lasting 7 days) if pregnancy of the first, and 5,5 months (22 weeks) at povtornoberemenny and get the estimated penal of childbirth. But it is worth making a reservation and telling that this sign has only auxiliary value. The reason that the feeling of stir of the kid in a womb is very subjective and depends on several factors among which:

an emotional condition of the woman (if future mother is positively ready for the pregnancy, the probability that she will feel stir before estimated term is high

Level a beta - subjedinitsa of a horionichesky gonadotrophin (In - HGCh). When there is a conception, the impregnated ovum shares, and in the course of this division the germ and fetal covers, one of which is called horion, develop. horion develops HGCh which is found in blood test. Already on 6 - 8 - y day after fertilization the level of this hormone is defined in blood of the pregnant woman.

, From where such accuracy? Let`s consider: 2 days - for fertilization. 4 days - advance of the impregnated ovum on a uterine tube and 2 days - on implantation (an attachment to a uterus wall). The maximum concentration of this hormone in blood are noted in 8 - 10 weeks of pregnancy. Thus, to different terms of pregnancy there correspond the HGCh levels in blood.

Ultrasonic research. The most reliable information at diagnostics of pregnancy and determination of its terms is received at early ultrasonic research (ultrasonography). At transabdominal scanning (when the sensor is installed on a forward belly wall) existence of pregnancy can be established with 5 - 6 - y weeks, at a transvaginal ekhografiya (research through a vagina) - on 1 - 1,5 weeks earlier.

a number of methods for determination of term of pregnancy Exists.
When the delay of periods is still absolutely small

(to of 7 - 10 days), OUSE - diagnostics of pregnancy depends on qualification of the doctor and quality of the equipment. In early terms the diagnosis of pregnancy is established on the basis of definition in a cavity of a uterus of fetal egg, a zheltochny bag, embryo and its warm reductions, and in later terms - on the basis of definition of a fruit (or fruits - at polycarpous pregnancy) in a uterus cavity.

Depending on information obtained at ultrasonography for the first time of week can assume this or that term of pregnancy. So, fetal egg of a rounded or ovoidny shape with a diameter of of 5 - 6 mm begins to decide on 3 - y weeks from the conception moment in a cavity of a uterus. In 4 - 5 weeks identification of an embryo is already possible - on the monitor it is defined as a strip of 6 - 7 mm in size. the Head of an embryo is defined with 8 - 9 - y weeks of pregnancy. it is important to p to remember

that only on early terms the embryo grows in proportion to the estimated term of pregnancy therefore at all women with identical term its sizes will be identical. The size of a fruit is informative for establishment of pregnancy term on it at most to 15 - y weeks, later hereditary features can already influence this indicator.

the Most exact indicator of term of pregnancy in the first trimester is kopchikotemenny the size (KTR). The mistake in establishment of term of pregnancy at determination of the kopchikotemenny size in 80% of cases does not exceed 1 day, and in 20% - 3 days. At the same time the accuracy of definition increases at calculation of an arithmetic average of three consecutive dimensions of KTR.

the term of pregnancy is established by

In the second and third trimesters on the basis of determination of various fetometrichesky parameters: bipariyetalny size, or cross size of the head of a fruit (BPR), head circle (HC), average sizes of a thorax and stomach, stomach circle (SC), femur length.

From the listed measurements in the second trimester the most informative for determination of term of pregnancy is BPR and a circle of a head. At the same time the more pregnancy term, the is less accuracy of its definition. For determination of term of pregnancy the ultrasonic research conducted to 24 - y is considered optimum weeks.

needs Separately to tell

about the fruit cerebellum sizes. The most reliable the method of determination of term of pregnancy by the mezhpolusharny size of a cerebellum which accuracy reaches of 1 - 2 day is considered. the Size of a cerebellum not only allows to establish most authentically the term of pregnancy and PDR, but also plays a large role in diagnostics of such terrible complication of pregnancy as a fruit growth inhibition syndrome.

the sizes of a cerebellum of a fruit are not influenced by the pathological processes influencing development of all bodies and systems of a fruit. The cerebellum is well protected, and it in the last turn reacts to change of a blood-groove. Thus, at fetometrichesky indicators there is less norm and the normal sizes of a cerebellum (corresponding to the gestational term of a fruit) the diagnosis “a syndrome of an arrest of development of a fruit“ is made.

Plans and reality

But here “treasured“ day came, and the kid also does not think to ask outside. To wait, go to the doctor or all - to go to maternity hospital? Independently it is possible to wait for no more than a week, i.e. to pregnancy term 41 weeks, then it is necessary to visit the doctor. The doctor will define readiness of an organism of the woman for childbirth (unripe or insufficiently mature neck of a uterus, decrease in a tone and excitability of a uterus in response to survey), and also will consider a condition of a fruit, in the absence of signs of patrimonial activity will direct to hospitalization in withtatsionar where future mother will be under continuous supervision. After carrying out a number of diagnostic procedures the issue of term and a method of a rodorazresheniye will be resolved.

Should not hurry time - everything will occur when it has to occur. Only in certain cases, when there is a need, the term of childbirth is appointed by the attending physician in an individual order.