Determining gestational age

Determining the gestational age is the most pressing issue for a woman who has recently learned about her interesting situation. Let's look at how to determine the gestational age, as well as the most accurate methods for determining the age.

Determining the gestational age is not only a pregnant woman's task, but also a gynecologist's. Since a correctly determined gestational age will allow you to monitor the course of pregnancy, prescribe the necessary tests and monitor the baby's development. Knowing the gestational age allows you to calculate the date of birth and maternity leave. And for the expectant mother, knowing the exact date of the baby's birth helps her mentally prepare for future motherhood and prepare everything necessary for the future child.

Gynecologists claim that knowing the exact gestational age is one of the main aspects of monitoring and managing pregnancy. Methods for determining the gestational age and the accuracy of their results allow you to monitor the intrauterine development of the baby and prevent various pathologies. We offer you the most modern methods for determining the gestational age, as well as special calendar methods that will allow you to independently determine the gestational age.

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Determination of pregnancy at early stages

Determining pregnancy at an early stage is important for a woman. Thus, almost 50% of embryos die in the first two to three weeks from the moment of conception. This happens because the embryo is defenseless against infection, which may be in the mother's body due to bad habits and other negative factors. Taking medications, smoking, prolonged exposure to the sun and drinking alcohol are the most common causes of embryo death in the first months of pregnancy. Many women may not know about their condition and continue to lead a lifestyle that is fatal for the development of the embryo.

Early pregnancy detection is also necessary for women who are planning to have an abortion. Since late-term abortion can lead to future infertility and serious complications. Medical abortions are performed during the first four to six weeks of pregnancy, and vacuum aspiration or mini-abortion is performed within 20 days after a missed period and confirmation of pregnancy. Classic abortion (curettage) is performed before the 12th week of pregnancy. But the optimal period for abortion and maintaining a woman's health is considered to be 6-8 weeks.

The onset of pregnancy is determined by various signs, both changes in the appearance and behavior of the pregnant woman. Frequent mood swings, vulnerability, changes in taste preferences, increased sensitivity, nausea (especially in the morning), swelling of the extremities, delayed menstruation and swelling of the mammary glands may indicate pregnancy at an early stage.

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Methods for determining the gestational age

Methods for determining the gestational age allow you to determine how much time is left before the birth and how the future child is developing. Let's look at the most popular methods for determining the gestational age.

• According to menstruation and the results of a gynecological examination. In the early stages of pregnancy, the uterus increases to the size of a chicken egg.
• According to ultrasound data, the accuracy of determining pregnancy using ultrasound examination is quite high in the first trimester.
• By ovulation - the pregnancy period can be determined by the date of the expected conception, adding 14 days to it. The date of birth is also determined by this method. To do this, three months and seven days are counted from the date of ovulation.
• According to bimanual examination – this method allows determining the gestational age by palpating the position of the uterus. In the first trimester, the uterus is located in the pelvic area, and starting from the second trimester, it is palpated above the pubis.

Pregnancy Duration Test

A pregnancy test is a modern method to find out the period before visiting a gynecologist. The most popular test among expectant mothers to determine the period of pregnancy is Clearblue. The test is easy to use and gives a result with an accuracy of up to 99%.

The test for determining the period works on the same principle as a simple express test for determining pregnancy. To get the result, you need to dip the test into a container with urine or urinate on it. After a couple of minutes, an hourglass and the result - the pregnancy period - will appear on the electronic test board. The only drawback of the test is that the board with the result goes out after 24 hours. Therefore, if you want to share the result with your friends and relatives, you should hurry.

Clearblue with pregnancy term determination

Clearblue with pregnancy term determination is a digital test that shows a double result on a special Smart Dual Sensor touch screen. So, with the help of the test, you can not only confirm pregnancy, but also find out its term. Let's look at the advantages of the Clearblue test.

• Now there is no need to look at the strips on the express test, as the digital display will show a reliable result that will last for 24 hours.
• Clearblue is the only test of its kind that provides information on the gestational age, i.e. the amount of time that has passed since conception.
• The test gives a 99% accurate result from the first day of delay.
• The test is very simple and easy to use.
• Clearblue has received approval from obstetricians and gynecologists worldwide.

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Determining the gestational age of a child

Determining the gestational age of a child is done by several methods. Some methods are based on the date of the last menstruation and the duration of the delay, others on the signs of pregnancy that a woman shows, and others make it possible to find out the gestational age using a digital test. Another way to determine the gestational age of a child is to undergo a gynecological examination or ultrasound. Each woman decides for herself which method to use. On average, about seven days pass after conception until the sperm fertilizes the egg. That is why many women focus on the ovulation period. Please note that it is recommended to plan pregnancy based on the ovulation period.

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Determining the gestational age by ultrasound

Determining the gestational age by ultrasound is one of the most reliable methods. Using ultrasound in the first weeks of a missed period allows you to accurately diagnose the gestational age. Ultrasound is used not only to determine the gestational age, but also to monitor the course of pregnancy and the development of the baby. Many gynecologists claim that the optimal period for reliable diagnosis of pregnancy is considered to be up to 6 weeks. Diagnosis of the gestational age by ultrasound at a later period will be difficult.

The results of the ultrasound examination in the first weeks after conception are based on the length of the embryo. The gynecologist measures the length of the fetus and compares the obtained data with the table values. This allows you to accurately determine the gestational age and monitor its progress. Throughout the pregnancy, the woman should do control ultrasounds so that the gynecologist can monitor the development of the child and, if necessary, prevent the development of pathologies.

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Determining the gestational age by weeks

Determining the gestational age by weeks is the task of the gynecologist. Knowing the exact gestational age, which is calculated in weeks, the gynecologist monitors the development of the child and the course of the entire pregnancy. In addition, depending on the period, the doctor prescribes certain tests and examinations that will help prevent the development of pathologies and complications in the child.

Pregnancy weeks are divided into obstetric (by which observation is conducted) and embryonic. The obstetric period is 40 weeks, and the embryonic period is 38 weeks. To determine the exact period, the gynecologist observes the symptoms of pregnancy and the development of the embryo.

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Determining the gestational age by menstruation

Determining the gestational age by menstruation is used most often, since this method is quite simple and effective. During an examination by a gynecologist and determining the gestational age, the doctor will learn the date of the last menstruation and the duration of the cycle. This data allows determining the gestational age by menstruation. Gynecologists use the method of counting pregnancy from the first day of the last menstruation. Since it is almost impossible to determine the exact date of conception, and menstruation is the only reference point.

When determining the gestational age, gynecologists use a calculation formula based on a 28-day menstrual cycle. This allows us to assume that ovulation occurred on the 14th day from the start of menstruation. But this formula is not always accurate, since not all women have a regular menstrual cycle. Therefore, determining the term has an error. Gynecologists distinguish two gestational age periods, the first is obstetric (from the first to the last day of menstruation), and the second is embryonic (from the date of fertilization and ovulation).

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Pregnancy Duration Determination Table

The pregnancy term determination table allows you to visually look at the expected date of birth and the pregnancy term. The table is based on the results of tests and gynecological examinations. There are several criteria that serve as the source material in the pregnancy determination table: fetal size, date of the last menstrual period and diagnostic results.

We offer you a table for determining the gestational age based on the results of an ultrasound examination, i.e. based on the size and weight of the fetus. The size and weight of the embryo in the first trimester are not taken into account in the table, as they are too small. Please note that the table for determining the gestational age uses obstetric weeks of pregnancy.

Week	Height (cm)	Weight(gr)		Week	Height (cm)	Weight (gr)
11	6-8	10-15		26	33.5-35.5	850-1000
12	8-10	15-20		27	35.5-37	1000-1200
13	10-12	20-30		28	37-38.5	1200-1350
14	12-14	30-50		29	38.5-40	1350-1500
15	14-16	50-75		30	40-41	1500-1650
16	16-18	75-115		31	41-42.5	1650-1800
17	18-20	115-160		32	42.5-43.5	1800-1950
18	20-22	160-215		33	43.5-44.5	1950-2100
19	22-24	215-250		34	44.5-45.5	2100-2250
20	24-26	270-350		35	45.5-46.5	2250-2500
21	26-27.5	350-410		36	46.5-48	2500-2600
22	27.5-29.5	410-500		37	48-49	2600-2800
23	29.5-31	500-600		38	49-50	2800-3000
24	31-32	600-750		39	50-51	3000-3200
25	32-33.5	750-850		40	51-54	3200-3500

Determining the exact period of pregnancy

Determining the exact gestational age can be done by several methods. Each of them has an error, let's look at the most popular ones.

• Symptomatic - the pregnancy period is determined by certain symptoms. Thus, breast enlargement, absence of menstruation and increased sensitivity indicate an early pregnancy. However, this method is quite controversial, since in some cases the above symptoms may indicate complications in the female body, and not pregnancy. That is, the accuracy of this method is 50%.
• Ultrasound examination is a popular method for determining the gestational age. The accuracy of ultrasound results in determining the gestational age is 100%.
• Digital tests are a modern method of determining the pregnancy period. The accuracy of the tests is 99%.
• Gynecological examination is the most accurate method for determining the period. Using examination and test results, the gynecologist determines the pregnancy period. The accuracy of this method is 100%

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Pregnancy Duration Calendar

The calendar for determining the pregnancy period is based on the Naegele formula. Nine months and seven days of pregnancy are added to the date of the last menstruation (its beginning) and three months are subtracted. Seven more days must be added to the resulting date, the result is the preliminary date of birth. According to this formula, there is a special calendar.

If you do not trust the calendar method, you can check its effectiveness. Calculate the date of birth using the calendar and compare it with the one that the gynecologist tells you after the examination. Please note that fetal movement is of great importance when determining the gestational age. It is with the help of the date of movement that you can calculate the exact date of birth. In this case, for women who give birth for the first time, 22 weeks are added to the date of movement, and for those who have given birth again, 20 weeks.

Determining the gestational age by hCG

Determining the gestational age using hCG is one of the most accurate methods. hCG or human chorionic gonadotropin is a protein hormone that is produced by the embryonic membranes throughout the pregnancy. It is hCG that blocks the processes in the female body responsible for the menstrual cycle and increases the production of hormones that are responsible for maintaining pregnancy. hCG increases during conception and is one of the reliable signs of pregnancy. The hCG level increases from the first week of pregnancy, that is, within 14 days after conception. This indicator doubles every day, starting from the 3rd week of pregnancy and up to the 12th week. From the 12th to the 22nd week, the hormone level does not increase, but from the 22nd week it begins to rise again.

The rate of increase of hCG in the blood makes it possible to determine deviations in the development of pregnancy. Thus, in case of a frozen or ectopic pregnancy, hCG is below the norm. And a sharp increase in this indicator indicates multiple pregnancy or chromosomal diseases. Therefore, the gynecologist, as well as the pregnant woman herself, should monitor the dynamics of hCG concentration in the blood during pregnancy. Let's consider the norms of hCG content and the effect of this hormone on determining the gestational age.

Days since last menstrual period	HCG levels for this period honey/ml	Pregnancy period
26 days	0-50	12 days
27 days	25-100	13 days
28 days	50-100	2 weeks
29 days	100-200	15 days
30 days	200-400	16 days
31 days	400-1000	17 days
32 days	1050-2800	18 days
33 days	1440-3760	19 days
34 days	1940-4980	20 days
35 days	2580-6530	3 weeks
36 days	3400-8450	22 days
37 days	4420-10810	23 days
38 days	5680-13660	24 days
39 days	7220-17050	25 days
40 days	9050-21040	26 days
41 days	10140-23340	27 days
42 days	11230-25640	4 weeks
43 days	13750-30880	29 days
44 days	16650-36750	30 days
45 days	19910-43220	31 days
46 days	25530-50210	32 days
47 days	27470-57640	33 days
48 days	31700-65380	34 days
49 days	36130-73280	5 weeks
50 days	40700-81150	36 days
51 days	45300-88790	37 days
52 days	49810-95990	38 days
53 days	54120-102540	39 days
54 days	58200-108230	40 days
55 days	61640-112870	41 days
56 days	64600-116310	6 weeks

Please note that the values indicated in the table are not a standard. Thus, depending on the characteristics of the woman's body and the course of pregnancy, the hCG norms for determining the gestational age also change.

Determining the gestational age by conception

Determining the gestational age by conception involves calculating the period by weeks. On average, pregnancy lasts 280 days or 40 weeks. Obstetricians determine the gestational age by menstruation and this is called obstetric weeks of pregnancy. But determining the gestational age by conception is called the embryonic period, and it is based on the ovulation period. Each woman conceives at a different ovulation period, so when determining the date of birth by conception, it is recommended to add 38 weeks to the date of the last menstruation.

But do not forget that obstetricians keep their own gestational age, which differs from the embryonic (gestational age at conception). And all tests will have to be taken, focusing on the obstetric gestational age.

Determining the period of pregnancy by ovulation

Determining the pregnancy period by ovulation is a simple and effective method. Ovulation is the period of menstruation in which pregnancy can occur, as the mature egg leaves the ovary and is ready for fertilization. On average, ovulation occurs on the 14th day with a normal menstrual cycle of 28 days, and in women with a long cycle, ovulation occurs between the 15th and 18th day. To accurately determine the ovulation period, you can buy a special test or measure your basal temperature. But some women can determine ovulation by certain symptoms (pain in the lower abdomen, increased vaginal discharge, increased sexual desire).

But the most accurate way to determine the pregnancy period by ovulation is an ultrasound examination. Ultrasound allows you to accurately determine ovulation. However, regular ultrasound is an expensive pleasure, so other simpler methods are used to determine the pregnancy period.

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Determination of the gestational age by CRL

Determining the gestational age by CTE is only possible with the help of an ultrasound examination. At the beginning of pregnancy, a woman undergoes an ultrasound examination, during which measurements of the ovum are taken. CTE is the coccygeal-parietal size of the embryo, which can be measured using visualization obtained by ultrasound examination. CTE is the maximum distance from the coccyx to the crown. The CTE indicator is used to determine the exact gestational age during the first trimester. Let's look at these indicators:

CTE value, mm	Pregnancy period, weeks
3	5
6	6
10	7
16	8
23	9
31	10
41	11
53	12
66	13

If the exact gestational age needs to be determined in the second or third trimester, other indicators are used instead of the CRL. Of great importance is the biparietal size or BPD, that is, the size between the temporal bones. Another indicator for determining the exact gestational age is the girth of the pregnant woman, the length of the thigh or femur. Let's consider the values of these indicators and the gestational age. Fetometric parameters in the second and third trimesters of pregnancy:

Biparietal size, mm	Abdominal circumference, mm	Femur length, mm	Pregnancy period, weeks
24	61	12	14
28	72	16	15
32	78	20	16
36	96	24	17
39	108	27	18
43	120	30	19
47	138	33	20
50	144	36	21
53	162	39	22
56	168	41	23
59	186	44	24
62	198	46	25
65	204	49	26
68	216	51	27
71	228	53	28
73	240	55	29
75	248	57	30
78	259	59	31
80	270	61	32
82	278	63	33
84	288	65	34
86	290	67	35
88	300	69	36
89	306	71	37
91	310	73	38
93	324	74	39
94	325	76	40

All the above indicators are used by modern ultrasound devices to determine the gestational age. But, do not forget that the indicators may differ from the real ones. Thus, when measuring the CTE, the error can be one week of pregnancy, and when receiving the BPD, the error is up to 11 days.

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Formula for determining the gestational age

The formula for determining the gestational age is used by many women. Let's look at the most accurate and popular formulas.

• Naegele's formula for determining the date of birth based on the last menstrual period
• To calculate, you need to know the date of your last menstruation and subtract three months and seven days from it.
• Jordania formula

The formula itself looks like this: X=L+C, the value of X is the gestational age in weeks, L is the length of the embryo, and C is the size of the head measured by a pelvimeter. Let's consider this formula in practice. L is 18 cm, C is 12 cm, that is, X=18+12= 30 weeks of pregnancy. But according to research, this formula has an error of 2 weeks.

• Skulsky's formula

This formula allows you to accurately determine the gestational age in the last trimester. So, the formula: X = ((Lx2)-5)/5, where X is the obstetric gestational age, L is the length of the embryo, 2 is the coefficient that allows you to determine the length of the fetus, 5 in the numerator is the coefficient of the thickness of the uterine walls, in the denominator is the indicator from the Haase formula.

• Haas formula

A formula developed by an obstetrician-gynecologist to determine the intrauterine age of the embryo during the first 20 weeks of pregnancy. In the first 20 weeks, the length of the embryo in cm is equal to the square of the months of pregnancy, in the last 20 weeks - the number of months of pregnancy multiplied by 5.

Accuracy of determining the gestational age

The accuracy of determining the gestational age depends on the method used and the characteristics of the pregnancy. To determine the exact term, the expectant mother will have to undergo many tests. The most accurate method is considered to be ultrasound, the use of digital tests and gynecological examination.

Determining the gestational age is important for every woman. Knowing the age of the embryo, the gynecologist can monitor its development, the course of pregnancy and prevent various pathologies and complications. In addition, the exact gestational age allows you to determine the date of future birth and prepare for meeting the baby.