What is the principle of calculating the date of birth?

1. What is the principle of calculating the date of birth?

Pregnancy lasts approximately 280 days (40 weeks) starting from the first day of the last menstrual cycle. The first day of the last menstrual cycle is the first day of pregnancy, even if pregnancy does not occur for a period of two weeks later (fetal development is delayed two weeks from the date of pregnancy usually).

Calculating the date of birth Due Date is not a precise science, where only a few women give birth at the estimated time, but it is important to take an idea of ​​when the child will be born roughly to help you to keep the baby healthy as well as public health mother.

2. How you can calculate the date of birth?

If the menstrual cycle is regular for women (ie 28 days) there are two ways to calculate the date of birth:

• Nigel base

Nigel's rule contains a simple equation: adding 7 days to the first day of the last menstrual cycle, and then subtracting three months, we get the estimated date of birth.

For example, if the date of the last menstrual cycle is November 1, 2019:

We add 7 days to date and become 8 November 2017.

We subtract three months and the date becomes 8 August 2017.

We change history when necessary, where history in our example becomes 2020 instead of 2019.

That is, the estimated date of birth in this example is August 8, 2019.

• Load wheel

Another way to calculate the estimated delivery date is to use the wheel of pregnancy, which is the method used by most doctors and it is very easy to calculate the date of delivery in the event of possession of such a wheel.

The first step is to put the date of the last menstrual cycle on the wheel, and when you place the cursor on that date, the wheel sets the expected date of birth.

Remember that these methods only estimate the time, and the chances of birth at this specific time are usually small but around that period.

What is the solution if you do not remember the date of the last menstrual cycle?

This situation is more common than you think, but fortunately there are ways to calculate the date of birth when the pregnant woman can not remember the date of the last menstrual cycle:

If the pregnant woman knows that the menstrual cycle was in a specific week, the doctor can estimate the date of birth roughly.

If you do not remember at all, your doctor will perform ultrasound to determine the age of pregnancy and when you will be born.

What is the solution in the event of an irregular or somewhat long cycle?

Some women have consistently longer menstrual cycles than usual. In these cases, the load wheel can still be used but with some simple calculations.

The second stage of the menstrual cycle continues for 14 days, the time between ovulation and the subsequent menstrual cycle. If the menstrual cycle for women is 35 days, for example, ovulation will be approximately 21 days of the menstrual cycle.

As long as we have a general idea of ​​the date of ovulation in general, the date of the last menstrual cycle can be used to determine the date of birth on the wheel of pregnancy.

For example, if the duration of the menstrual cycle is 35 days, and the first day of the menstrual cycle is 1 November (1/11 November 1):

We add 21 days (date becomes 22 November).

We offer 14 days to find the adjusted date for the last menstrual cycle (here November 8).

After calculating this date, we calculate the estimated birth date on the load wheel as before.

3. Why can a doctor change your expected date of birth?

The doctor may change the expected date of birth if the fetus is smaller or larger than the mean age according to gestational age.

The doctor conducts ultrasound to determine the gestational age in the case of irregular ovarian cycles, if the last date is uncertain, or when pregnancy occurs despite oral contraceptives.