Methods of determine gestational age and date of birth


2018-03-17 15:01:12




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Many women learn that they are in an interesting position, begin to dream of the day when the child is already born. The precise definition of pregnancy and childbirth is possible only if the conception was in vitro, i.e. in laboratory conditions. However, doctors in all other cases, however, are able to determine the expected date of birth of the child and they have their own methods.

Is it Possible to calculate everything exactly?

pregnancy Test

The Determination of gestational age occurs most often on the basis of ultrasound or on the basis of the exact date of the last critical days. Despite the fact that modern medicine has stepped far forward - only 4% of babies are born at predicted date, with 96% of children appearing for a couple of weeks earlier or even later on the designated day. Why things happen this way? Methods for determining pregnancy and delivery date allow us to calculate the approximate date, the period of pregnancy can vary from thirty seven to forty two weeks, and all the children that appeared in this time period are chargeable on the date of maturity.

Keep in mind that after defining the duration of pregnancy and date of future delivery, correct to assume that the birth of a baby can occur during the period that begins two weeks before the deadline and for a week afterwards. Always keep this in mind and don't worry.

What is the definition of pregnancy in the last month?

counting down the days before the onset of menstruation

How everything happens? During the initial visit to the obstetrician-gynecologist, he asks when was the first day of your last menstrual period. Then the doctor to determine the period of pregnancy for the last month uses the formula Negele. What is the formula? For the calculation shall be the first day of the last critical days, it is taken away three months and added to the date seven days. If the menstrual cycle is less than twenty-eight days from the received date will need to take the difference (e.g., three days, if the cycle lasts twenty-five days). If the cycle is longer than a couple of days, the difference is added to the expected date of birth.


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Accurate is this method of determining pregnancy by month? This technique is applied, if a woman regularly maintains a calendar of your menstrual cycle and remembers the exact beginning and end of menstruation. However the problem is still there, because in normal condition, the pregnancy can last from thirty eight to forty two weeks, because the inaccuracy will be. Yet it is worth noting that the method only works when the expectant mother is not observed problems with the cycle. It needs to be stable, uniform and last exactly 28 days. In such situations, the pregnancy is likely to last 280 days or, if to speak medical language, obstetric ten months, starting from the first day of the last menstrual period.

Determine pregnancy for ovulation

Pregnant woman holding belly

The Definition of term pregnancy to delay ovulation is quite straightforward. With a cycle length of 28 days ovulation occurs around 14 th day. To this day we add 38 weeks and all. This will be the day of birth. Accurate is this method? The fact that many women, the cycle is unstable and has inconsistent or down. The interval between periods can be 25 days, and can reach 32-33 days. How to determine the day of ovulation? It begins 14 days before your next period, however, these calculations are not always accurate. All due to the fact that the ripened egg lives a few days, and sperm can live inside the female body for up to five days after intercourse. This method of determining pregnancy works best if the time interval between sexual acts was not less than 6 weeks.

Ultrasound as a method of pregnancy

Pregnant girl at the doctor

How it is calculated? Based on many years of research and observations was compiled a special table, in which the pregnancy is matched with the fruit (taken distance from tailbone to top). Also takes into account head circumference, chest and even thigh length. Is it possible the definition of early pregnancy? Of course, but in such cases, does the size of the ovum.

Accurate is this method? Currently, this technique is considered the most accurate. The question arises: “At what point in the pregnancy to determine the due date it is permitted to apply?” it is better to use ultrasound during the period from 4 to 13 weeks. In this period of time the size of the fetus in women actually no different, because to set the duration of the pregnancy is possible even with precision to hours. However, one should not forget that the later will be measured, the greater the error. Note immediately that in the second and third trimester the fetus depends on many factors: heredity, genetics, nutrition of the mother and so on. Because kids sizes may vary, and the due date can be set exactly.

Survey Results for the establishment of pregnancy

Once you appear on the doctor's examination, the specialist will try to assess the size of the pregnant uterus, and in particular the standing height of the bottom to determine pregnancy. Accurate is this method? Experienced doctors are not magicians. The size of the uterus and the height of the bottom in most cases depends on the size of the baby, amount of amniotic fluid, presence of pathologies, and so on. The smaller the gestational age, the easier it will be to measure and determine the date of appearance of the baby born.

How to install a pregnancy at the height of the uterine fundus?

Pregnant girl

The Determination of gestational age is carried out by inspection of the uterus. The height of the uterine fundus or abbreviated as VDM – is the distance between the upper area of the pubic articulation and the upper part of the uterus that protrudes from the pelvic cavity. When the fruit begins to grow, the uterus will increase and, since the end of the 4th obstetric months, or 16 weeks, the fundus can already be measured through the abdominal wall. Up to this period, the growth of the uterus specialist sets only at vaginal examination.

Measure the height of the uterine fundus be at every doctor's visit, from 16-weeks. Before this is possible the approximate determination of gestational age by month, or by any other method.

How the process of measurement? The woman lies on the couch, straightens his legs, it is desirable that the bladder was empty. The doctor, once the patient has laid down, carries out measurements of the height of standing of bottom of uterus with the tape measure. The study will take no more than a minute, but it will allow us to judge the nature of the growth of the baby, position, and amount of amniotic fluid.

Of Course, there is the generally accepted values of VDM, which correspond to each term of the pregnancy, but you always want to consider many factors and what is an individual indicator, which can vary within three inches.

Always, spending this kind of analysis for the determination of gestational age, pay attention to how VDM is increased in comparison with the previous indicator. Already in the 24th week of pregnancy, the event will coincide with the term of pregnancy.

If VDM is below normal, then this may indicate the following factors:

  • An error has occurred in the definition of pregnancy in the early stages;
  • The availability of a wide pelvis in large women;
  • Delay in fetal development;
  • Reduced volume of amniotic fluid.

If the event is larger than normal, it indicates the following:

  • The fruit is very large;
  • Multiple pregnancy;
  • The mother's pelvis narrow;
  • A fetus is wrong;
  • The volume of amniotic fluid is increased.

Also to monitor the status of the fetus, its growth and volume of amniotic fluid was performed measuring the abdominal circumference at the navel. The indicator depends on the individual characteristics of the expectant mother, thickness of subcutaneous fat, therefore takes into account the dynamics of the increase in circumference. These parameters allow us to determine the possible weight of the child. For this you will need to multiply the number of WMM coolant. For example, VDM equals 36 inches, and coolant – 95 centimeters, then it turns out that the possible weight of the baby will be approximately 3420 grams. If the indicators do not correspond to the VDM on the term three centimetres and more, the doctor prescribes additional examinations. Held ultrasound, dopplerometry and cardiotocography, and then, on the basis of the obtained results, a treatment is installed and the tactics of the upcoming birth.

The Dependence of VDM from pregnancy.

Period in weeks



The uterus is the size of a chicken egg


The Uterus to the volume of a goose egg.


Alin Trodden - author of the article, editor
"Hi, I'm Alin Trodden. I write texts, read books, and look for impressions. And I'm not bad at telling you about it. I am always happy to participate in interesting projects."

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