Gynecological examination method
A routine obstetric examination allows an experienced doctor to determine the week of gestation, and based on this, to calculate the date of the upcoming birth. The main thing that a gynecologist determines during an examination is the height of the fundus of the uterus and the degree of its increase in the process of bearing a child. The height of the uterine fundus is measured at each visit to the antenatal clinic to monitor the development and course of pregnancy.
The uterus should grow in accordance with the growth of the fetus. From the 16th obstetric week, fundal height can already be measured transabdominally; before this period, the uterus is examined and its growth rate is determined during vaginal examination. A simple examination using a regular measuring tape allows not only to determine the height of the uterine fundus, but also to assess the growth of the fetus, determine its position, and judge the volume of amniotic fluid. A few days before birth, the uterus lowers by 3 cm due to the fact that the baby's head takes a position in the pelvic cavity.
Other calculation methods
There are at least 5 types of traffic allowance calculations.
By conception
The most common calculation. A woman's menstrual cycle is divided into three phases: follicular, ovulatory and luteal. In these phases, preparatory processes for the birth of a new life in the female body occur. Maturation of follicles, eggs (ovulation) and fertilization of the egg.
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If a woman knows exactly when she will ovulate, then after conception she can easily calculate the day and month the baby is due.
The menstrual cycle lasts on average 28 – 35 days. The maturation of the egg occurs in the middle of these intervals. But in order not to be mistaken in the dates, it is better to purchase an ovulation test strip at a pharmacy and insure yourself.
Upon first appearance at the antenatal clinic
A visit to the antenatal clinic for examination by a gynecologist, where a specialist, with a high probability, using a blood test and uterine enlargement, can find out the patient’s time of delivery.
During gestation, the uterus changes its size. A hormone responsible for the successful bearing of a child, human chorionic gonadotropin, appears in the blood.
This hormone appears 6-8 days after conception and is intensively produced until the end of the first trimester.
If during this period, during a subsequent blood test, the hormone slows down its growth or sharply decreases, then you should pay special attention to this.
This phenomenon threatens spontaneous miscarriage or ectopic pregnancy.
When receiving the test result, you should carefully review the laboratory table, which indicates the embryonic gestational age. Then we add 2 weeks, thus calculating the expected obstetric due date.
Find out the time of birth by ultrasound
Currently, the most accurate means of calculating the due date is ultrasound. It determines PDR with maximum accuracy and, which is very convenient, this procedure can be carried out at a short period in the first trimester.
Thanks to a competent diagnosis by a specialist, future parents will be able to find out at what period their miracle will appear.
Determination of PDR using ultrasound examination occurs according to the following parameters:
- Using ultrasound sensors, an image from the uterine cavity is transmitted to the screen. After carefully examining the image, the specialist determines when fertilization occurred and the time of pregnancy.
- If for some reason an ultrasound was not done in the first trimester, it does not matter. The planned date of birth may be determined in the second and third trimesters. Using photometric proportions: the size of the coccyx and crown, the most convenient indicator in the first three months. Biparietal size, it is used in the second half of pregnancy.
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But in order to establish a more accurate time of birth, it is necessary to do an ultrasound examination in the first trimester. Since in the early stages the embryo grows proportionally in all women, and in the late stages the development of the baby occurs exactly the opposite.
Children may be the same age, but they will differ in size and therefore the baby’s due date may not be accurate.
At the first movement of the fetus
Calculating the estimated time of birth of a baby based on fetal movements is a method that has long lost its relevance. But there are still mothers who use this method.
This method is based on the fact that, on average, the baby makes its first kicks at 20 weeks. For mothers who have felt the joy of motherhood not for the first time, the initial impulse of the child is caught at the beginning of the 18th week.
It is for the purpose of fixing the starting point that the doctor who is observing the pregnant woman recommends remembering the first statements about the existence of the unborn child.
The gynecologist records the time of the first push on the exchange card. Based on this, he calculates the MDR. If this is your first pregnancy, you should add 20 weeks to the push date.
When the pregnancy is secondary, or maybe more, then it is necessary to add 22 weeks.
But as mentioned above, this method has a high error and is not particularly popular among both women and doctors. The body and lifestyle of each woman is individual.
Mothers who lead an active lifestyle feel fetal movements much later than those who have time to listen more carefully to their body.
Also, women who are in this position not for the first time, based on experience, can feel the baby moving already at 16 weeks. And inexperienced first-time mothers can confuse the baby’s first kick even with a strong spasm in the intestines.
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By date of last menstruation
In the case of using the last date of menstruation when determining PDR, the technique is widely used in the practice of specialized specialists.
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To calculate the expected date of birth, subtract three months from the start of menstruation. Next, you need to add 7 days to the resulting number. This is the time when uterine bleeding occurs.
After all the subtractions and additions, the estimated date of birth was obtained. But again, this method does not provide an exact guarantee that the child will appear exactly at the expected time, since the female body is individual, and it happens that the patient’s menstrual cycle is irregular.
When the duration of the menstrual period is 35 days and not the usual 28 days, then the expected date is calculated to be 21 days. For most women it is 14 days.
And if the preliminary date of birth is calculated based on the moment of the last menstruation, in this case it will be 7 days earlier than the actual one.
PDA by date of conception
This is also a rather controversial method, because the possibility of making a mistake in a specific date is very high. As you know, a woman can become pregnant only on certain days of the cycle, approximately 12-14 days. Even if sexual intercourse was a single act, say, on the 11th day of the cycle, then conception itself could well have occurred on the 12th day. This is due to the fact that sperm can live in a woman’s body for up to several days and “wait” until the egg is ready to accept them for fertilization. Therefore, it is quite possible to make a mistake with the date by a day or two.
Even knowing the date of possible birth, the child knows better than us when he should be born. Therefore, doctors set the estimated date of birth at 40 weeks, but the norm is considered to be the birth of a child from 37 to 42 weeks. And here, indeed, little depends on both the doctors and the woman herself.
There are many ways to determine the likely date of birth of your baby. Today, the most reliable of all known methods is counting according to the menstrual cycle. Its essence is quite simple: three months are subtracted from the first day of the last menstruation, and then one week is added to the resulting date.
Another very accurate method of determining the date of pregnancy is by the size of the fetus, which is detected using ultrasound. But it also has one significant drawback - the parameters of the fruits of different women differ quite greatly, so there is a high probability of error.
But even before the advent of ultrasound, the day of birth was calculated based on the baby’s first movement.
Determining the approximate date of birth during examination by a gynecologist
An obstetrician-gynecologist, examining a pregnant woman, determines the degree of enlargement of the uterus. This is what helps to predict the approximate date of birth quite accurately. The uterus grows along with the baby, so calculating the expected date of birth for an experienced specialist is usually not difficult.
Based on the size of the uterus in the first trimester of pregnancy, the doctor can calculate the gestational age, and then calculate the expected date of birth, based on the approximate date of the last menstruation.
In the second and third trimester of pregnancy, determining the approximate date of birth during an examination by a gynecologist can be difficult because the uterus increases in size in each pregnant woman with different intensity. That is why in later stages of pregnancy this method is considered ineffective.
The first fetal movements during pregnancy.
Determining the onset of labor by the first movement is often inaccurate, because the fetus moves from the 8th week of pregnancy, while the sensations of its movement are perceived by the expectant mother quite subjectively. Often, when expecting their first child, women mistake normal bowel movements for fetal movements.
In this method, the starting point is the moment when the expectant mother first feels the baby move.
Typically, a woman experiences fetal movement between 18 and 21 weeks of pregnancy. Much less often, however, it happens that this occurs both at 14 and 25 weeks. In fact, the timing of the baby’s first movement in the womb depends on the individual characteristics of the female body.
Women with a dense build are a little more difficult to recognize the first movements, unlike women with a slender figure. In addition, women whose pregnancy is their first simply do not know what exactly the sensations are during the process of intrauterine movement of the child. This is why they may not notice it right away. Women who have already given birth may well feel even earlier movement.
The first movement of the fetus also depends on the sensitivity and thickness of the uterine walls.
PDR for ultrasound examination
It’s worth noting right away that determining the exact duration of pregnancy and setting a more or less correct PDP is possible only after undergoing an examination up to 12 weeks. The reason for this is that everyone is different, starting from the womb. Some babies are born larger, others smaller, and everything is considered normal. Only when the child’s weight is above average is there a high probability that the doctor will set a term longer than the present one. For children whose weight is slightly less (the reason for underweight may be both intrauterine growth retardation and the child’s physique), the doctor may mistakenly assign a slightly shorter period.
To indicate the correct period, it is important to undergo at least one ultrasound before 12 weeks. During the examination, the doctor can determine the weeks with an accuracy down to the day. Later, during other examinations and examinations, it will be possible to build on the indicators of the first ultrasound.
Calculation of MDA by day of ovulation
It is a common and erroneous belief that pregnancy lasts 9 months. In fact, its duration should be calculated in lunar months, and the period will be 10 lunar months. In days, this period will be 280 days.
If the pregnancy is planned, you almost certainly know the date of your last ovulation and, accordingly, the date of conception. It is to this day that you need to add 280 days, which will be the period when the long-awaited child is due to be born.
If you don’t know when ovulation occurred, but the cycle was stable, then you need to take exactly the middle of the last cycle and add the same 280 days to this day. But here a small error is possible, which should be counted on.
