Home Life The date of birth: methods for determining the date of birth

The date of birth: methods for determining the date of birth

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Date of birth: are there accurate methods of determining it?

The date of birth is the main thing about which women bearing children under heart worry. Every pregnant woman wants some certainty. Just learning about being pregnant, the future mother wants to know the date of expected birth. However, how to do it correctly? Many women try to calculate the date of birth by the date of conceiving. However, they do it in a not quite correct way, adding to the estimated date of conceiving 9 months to calculate the date of delivery. However, such a method of determining the date of birth by the date of conceiving is not entirely correct. Pregnancy does not last exactly 9 months and 280 days (10 lunar months). So how can you correctly identify the date of birth by the date of conceiving? Are there other methods of determining the date of delivery? Which way is the most accurate?

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Determination of the date of birth by the date of conceiving and ovulation day

As it is known, the female organism can conceive only during ovulation, when a mature egg is released from the ovary. Women’s menstrual cycle lasts on average 28-35 days. Ovulation occurs in the middle of the menstrual cycle. Knowing your ovulation date can make it easier to predict the date of the birth.

Some women feel their ovulation. During this period, they feel stabbing or aching sensation in the lower abdomen, the amount of vaginal discharge increases. Libido is also increased. And some even have slight spotting in the vaginal discharge. Ovulation can be determined with accuracy by ultrasonography.

However, how do you determine the date of birth if you do not know exactly the day of ovulation? To do this you can simply calculate your mid-menstrual cycle and to add this day 280 days. This way you’ll calculate the approximate date of the birth date by the date of conception.


For example, if your menstrual cycle is 28 days, ovulation occurs somewhere in the 12-14 day cycle. Add 10 lunar months (280 days) to the date of the alleged conception, and you’ll get an approximate delivery date. If you calculate the date of birth by the date of the sexual intercourse, then this option will be even more accurate, especially if there was just one sexual intercourse during the last menstrual cycle was a single.

However, it is worth remembering that the conception date may not coincide with the day the. Sperm can “live” in a woman’s body for up to several days. That means, if an unprotected sexual intercourse occurred on the 10th day of the cycle, ovulation and conception may have occurred on the 12th or 13th day. So, you should calculate the delivery date according to the date of conception, that is, starting from the day of ovulation.

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Determination of the date of birth based on the date of the last menstrual period

Coming to consultancy to a gynecologist, usually, the first thing the doctor asks is when was the last menstrual period. Young inexperienced girls, for the most part, do not pay attention to the regularity of their menstrual cycle and can not give an exact date. Others start to remember the date of the beginning and the end of menstruation. Although the doctor can determine the gestational age and the birth date knowing only the first day of your menstrual period. It is the day from which the menstrual cycle is counted and its duration is calculated.

determine date of birthThe simplest formula, to determine the date of birth is Negele’s formula. To calculate the delivery date we need to deduct 3 months from the first day of the cycle and add 7 days to it. For example, your last menses began on April 3.  Three months less is January 3. Now add 7 days to the January 3. It turns out to be January 10. This is the estimated delivery date.

However, this method of determining the date of birth is not always accurate. It is designed to determine the approximate date of childbirth for women whose menstrual cycle is exactly 28 days. If it is longer, and date of birth are likely to come later, and vice versa. This is because in case of a longer menstrual cycle, ovulation occurs later. And, in a shorter cycle, it happens earlier than 12-14 days, which was made according to the formula. In irregular menstrual cycles, it is very difficult to define the date of birth and using this formula to determine the date of birth is considered to be wrong.

Determination of date of delivery using ultrasonography

It is considered that the most accurate way to determine the date of birth is to use ultrasonography at early stages of pregnancy, up to 12 weeks. After having done ultrasonography at very early stages, you can find out the term of the pregnancy with accuracy up to one day, and calculate the approximate date of conception and the birth date.

The pregnancy age can be defined at the later stages of pregnancy as well. However, such ultrasonography results cannot be the basis for determining the date of childbirth, because all children develop differently, individually. In addition, some children are born weighing 5 kg and others weighing 3 kg. Both are the norm. However, in the first case, for women in the second and the third trimester, dates of birth are defined a couple of weeks later than the actual ones.

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Labors are likely to begin later, both doctors and the woman herself will rush the thing, thinking that the due date has already passed. And vice versa, short, thin parents have children of the same physical build. However, woman can be diagnosed with “intrauterine fetal development delay”. Defining the pregnancy age less than it really is, and thereby more correctly defined the date.ultrasound method

Defining an approximate date of delivery according to the results of gynecological examination

Gynecologist performing the manual examination of the female genitals, can determine pregnancy “by touch”. Pregnancy can be defined within the first 3-4 weeks. It’s worth knowing that at later dates (more than 12 weeks) stating the exact gestational age and determine the approximate date of delivery will be almost impossible. The reason for this is the same as when conducting ultrasonography lately that is each child develops differently, individually.

So, what does the gynecologist pay attention to when conducting the examination? Primarily, it is the size and shape of the uterus. Pregnant woman’s uterus acquires spherical shape and becomes larger in size. The more-or-less experienced gynecologist defines pregnancy age and the approximate date of birth, based on the size of the uterus.

Determination of date of birth at the later stages of pregnancy

There are times when it is difficult to determine the date of birth according to the date of conception. In such cases, you can take advantage of this proven technique, as the defining of the date of delivery on the date of the first movements of the baby.

The baby in the womb starts to make its first movement quite early, about 12 weeks. However, a pregnant woman does not feel them, since the baby is still quite small. The real movements a primipara begins to feel on the 20th week, multipara on the 18th week. Thus, to calculate the date of childbirth, in the first case, to the date of the first stirrings it is necessary to add 20 weeks, in the second case, we add 22 weeks.

Thus, we get almost the exact date of birth. Many women say that they begin to feel the first stirrings much earlier than the anticipated date, on the 16th or 14th  week. Gynaecologists usually do not take such statements seriously, explaining those movements of a baby as catastalsis of the bowels. Nevertheless, there are such sensitive women, in their case, the determination of the date of delivery on the date of the first stirrings of the baby will be incorrect.

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When is the right time

Somewhere between 14-16 weeks of gestation gynaecologist can accurately determine the pregnancy age. And the approximate date of birth with the help of the ordinary examination (not on the gynecological examination chair). By touching he will determine the height of the bottom of the uterus. Judging by that it is possible to define the pregnancy age and the date of childbirth without any calculations made from the date of conception. On the 16th  week, the bottom of the uterus is located between the pubis and belly button. On the 24th  week it is in the area of the navel, on the 28th week it is 4-6 cm above the navel.

There is another method of defining gestational age and date of birth. It is to measure the abdominal circumference. However, it isn’t very accurate because we are all different and the waist size is also initially different. Larger women, prone to obesity, will have the bigger volume of the stomach. In any case, than thinner women with the same date of birth will. Measuring the length of the uterus is much more informative for calculating the dates of the upcoming deliveries.

Why is the date of birth called not accurate but only approximate?

Actually, calculate the exact date of birth is not possible to calculate the exact date of birth even according to the date of conception. The causes of errors in calculation of the date of birth based on the date of conception, we have already reviewed at the beginning of this article. A relatively small percentage of women give birth just in time, determined by the gynecologist. Though it is said that pregnancy should last exactly 40 weeks. In many cases this is not true.

The date of delivery can also occur in 38 weeks and this is not the pathology either. Multiple pregnancy childbirth almost always occurs before the date defined by the gynaecologist. Other factors can influence the delivery date. Such as abounding in water, high pressure of the pregnant women, diabetes, etc. It is possible to calculate the birth date by date of conception by using an online calculator.


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