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After a pregnant woman becomes pregnant, in addition to the development of the fetus, the most concerned is the expected date of delivery.
There are two ways to calculate the expected date of delivery: one is based on the last menstrual date of the pregnant woman, and the other is calculated according to the result of ultrasound B.
The month of the last menstrual date of a pregnant woman plus 9 or minus 3 is the number of months of the expected date of delivery, while the number of days plus 7 is the estimated expected date of the pregnancy.
However, because some pregnant women will be more careless and do not remember which day they are pregnant, in this case, the doctor will estimate the approximate gestational age of the fetus according to the results of the obstetric examination and the physical development of the fetus, such as: double top diameter, femur length, abdominal circumference, so as to infer the expected date of delivery of the pregnant woman.
At 7-8 weeks of pregnancy, pregnant women can do early B ultrasound, so that doctors can calculate the gestational week of pregnant women according to the size of the fetus.
Head and hip length calculation week head and hip length is the distance from the fetus's head to the buttocks, 6-12 weeks when the measurement will be more accurate, more than 12 weeks, it is prone to error.
How do pregnant women calculate gestational age based on early B ultrasound? 3 ways for pregnant women to know
1. Head and hip length is calculated as gestational age
The head and hip length can also be used to calculate the gestational week of pregnant women, which is very convenient.
Gestational week = head and hip length CRL + 6.5, if the head and hip length is 1.9 cm, then the gestational week is 1.9 + 6.5 = 8.4, which is equivalent to 8 weeks and 4 days.
2. Gestational sac size is calculated as gestational age
If the gestational sac is 1.5*1.2, then the gestational week is 5 weeks and 5 days.
When pregnant women do B ultrasound, the doctor will measure the size of the gestational sac and write it on the B ultrasound list, so that the pregnant woman can calculate the gestational week of the pregnant woman by herself through the gestational sac comparison table.
3. Fetal size is calculated as gestational age
The size of the fetus is calculated at 10-13 weeks of gestational age, and the doctor will measure the double top diameter, abdominal circumference, femur length, head and hip length of the fetus, and calculate the gestational age of the fetus according to the values of these parts, so as to calculate the actual gestational age of the pregnant woman.
When is the B ultrasound check more accurate for actual gestational age?
Generally speaking, after a pregnant woman becomes pregnant, the doctor calculates the expected date of delivery of the pregnant woman through the last menstrual period of the pregnant woman.
However, some pregnant women can't remember the time of their last menstrual period, or the menstrual irregularity, the ovulation time is not fixed, so they need to pass the B ultrasound examination, according to the fetal development, calculate the gestational week of the fetus.
Pregnant early pregnancy is mainly to see the length of fetal buds, if the pregnant woman is early pregnancy, the pregnancy time is relatively short, then B ultrasound can only see the fetal buds, fetal sacs, yolk sacs, of which the length of the fetal buds can reflect the gestational age of the fetus.
At 28 days of pregnancy, the fetal bud is 4 mm, at 32 days of pregnancy, the fetal bud is 4.5 mm, and at 40 days of pregnancy, the fetal bud is 8 mm.
Early pregnancy - head and hip length calculate gestational week (7-12 weeks) Fetal buds slowly develop into a fetus that has just taken on human form, so that we can calculate gestational age using the length of the fetal head and hips.
Head-hip length is the distance from the fetus's head to the buttocks, and it is measured accurately at 7-12 weeks of pregnancy.
Actual fetal gestational week = CRL head-hip length (cm) + 6.5 If the fetal head-hip length is 6, then fetal gestational week = 6 + 6.5 = 12.5 = equivalent to 12 weeks and 5 days of pregnancy
Mid- and late pregnancy - fetal development index calculates the gestational week After the fetal development exceeds 12 weeks, it is no longer suitable to calculate the fetal gestational age with the length of the head and buttocks, because the various parts of the fetus's body have a certain development.
We can judge the corresponding gestational age of the fetus by referring to the values of the actual double top diameter, abdominal circumference and femur length of the fetus through the standard table of fetal development, which is more accurate.
Generally speaking, in the early stage of pregnancy, through the data of fetal B ultrasound, it will be more accurate to calculate the gestational week of the fetus.
In the second and third trimesters of pregnancy, because of the individual differences in fetal development, the degree of fetal fat and thin is different, so the fetal gestational error calculated by B ultrasound will be relatively large.