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How Does A Pregnancy Calculator Work?

You are pregnant. Congratulations! Your doctor might have informed you with the help of a pregnancy calculator. Now, you might be eager to know your due date. Well, However, some of you might be curious how they come to know when exactly your bundle of joy is about to arrive! So, let's take a look at various methods to calculate your due date.

Last Menstrual Period (LMP) Method

This is the standard method. You add 280 days to day one of your last menstruation. This method works on the classic 266-day pregnancy period plus 14 days. The latter is the time of the first day of menstruation till you would have ovulated. However, this pregnancy calculator might be erroneous; as the assumption is that you have ovulated 14 days after the commencement of your menstrual period and were fertilized exactly on that day.

Basal Body Temperature And Lutenizing Hormone (LH)

This is yet another pregnancy calculator. You keep a check on your basal body temperature or the surge of LH. It indicates the occurrence of ovulation, the time of intercourse, and the date of fertilization. If you are sure of your fertilization date, then you simply have to add 266 days to get your due date.

Naegle's Rule

This is a faster way to know your due date. Many doctors follow this pregnancy calculator. It takes into account the first day of your last period along with the standard gestation time. If you know this date, simply count three months back from your date and add 7 days to this. You will get your due date.


In an ultrasound test, sound waves are used to produce your baby's picture. When you are in the first trimester, your doctor may use ultrasound test to estimate your baby's age. On the basis of this, its due date can be calculated.

Remember; there's no accurate method of calculating the date of delivery. Mostly, they are calculated on the basis of averages; hence, they are hardly precise. It has been assumed by medical experts that, on an average, a baby remains in the womb for about 40 weeks. However, pregnancies may last a week or two earlier or later than this.

To get into some statistics, it has been found that about 80 per cent of mothers deliver within 10 days of their delivery date while 10 per cent of them deliver in less than 38 weeks. There are about 8 per cent babies who are born after 42 weeks. Quite a long stay in the womb!

Well, whatever may be the due date; forget worrying about the exactness of pregnancy calculator. Concentrate on enjoying each moment of your pregnancy. Good Luck!

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