How to calculate pregnancy due date

Most women get confused about number of day they have been in pregnancy, especially at initial stages. Its natural to be excited and anxious to know and keep tabs on each moment of pregnancy. However there is no way to know on when you ovulated and conceived.

This is the reason even health professionals tend to date pregnancy based on patients’s LMP (last menstrual period). Hence its crucial to monitor your periods closely and keep record of it and you have been planning for a baby.

Maintain a dairy of your period so that you remember exactly on your last period started. So first day your LMP is counted as “Day One” of your pregnancy. Thereafter use this pregnancy calculator to find out your estimated due date.

Calculation of Due Date – How Many Weeks Pregnant are You?

EDD (estimated date of delivery) is referred as “due date” and its expected date when you start labor actually. Since the date is an estimate, you start labor anywhere between 2 weeks before or after due date.

Only 1 in 20 pregnant ladies deliver exactly on due date. This is an indication that only 5 percent babies across globe are born on exact calculated date.

Fetal Age vs. Gestational Age

The term ‘gestation’ is used for defining time between actual concepton date and birth or time period woman is pregnant (in weeks). Measurement of gestational age is done starting from LMP to present week in date.

Mostly pregnancies last anywhere between 38 and 42 weeks. At case, baby is born before thirty seven weeks where he or she is considered a “preemie” or premature.

Fetal Age is different unit of measurement. Its done starting from gestational age. Gestational age is said to measure pregnancy span at weeks where Fetal Age is actual age of growing baby.

First Day of Last Period

Most pregnancies tend to be around 40 weeks. Some last for about 38 weeks from date of conception. Hence best or most accurate way to estimate due date is count 40 weeks or 280 days, starting from first day of your menstrual period (LMP),

Method 2

Ideal nourishment during pregnancy

There is another way to calculate pregnancy. You can just subtract 3 months from first day of your last period.

Date of Conception

Women must have regular menstrual cycle can calculate that their due date based on first day on last period. On other hand, if your cycle is not regular that this method doesn’t work.

Its crucial to have reliable estimated date of delivery (EDD). This is  how your doctor can estimate your conception date. For estimated due date that you need to add 266 days to it.

Irregular Periods/Forgotten Date of Last Period

As discussed already, due date works calculation works best if your menstrual cycle is regular. This means that you need to get period every 28 days. If your last period started on April 8th, you must need to count back 3months to 8th January. Add 7 days to result as January 15. This is how your healthcare practitioner which will estimate your due date.

Ultrasound Scan

This is a good way when you are unable to determine when you conceived. It helps when you forget the day of last menstrual period. An ultrasound which can help you and your practitioner determine due date.

An early ultrasound is the main to calculate the due date. The test is recommended if periods are irregular or the patient is 35 years of age or older. Ultrasound is a crucial step taken by health care practitioners if the patient has a history of miscarriages or complications in pregnancy.

Understanding a Trimester

The literal meaning of “Trimester” is “3 months”. Most pregnancies last for 9 calendar months. Each pregnancy is categorized into 3 trimesters. This is one of the best way to describe change inside a woman’s body.

First Trimester – It lasts from the beginning of your pregnancy until you are 13 weeks and 6 days pregnant.

Second Trimester – It lasts from 14 weeks to 27 weeks and 6 days of pregnancy. This is also known as the golden period where mother feels better, the bump starts showing, face glows and morning sickness fades off.

Third Trimester – This period lasts from 28 weeks of pregnancy until the baby comes out in this world.

How long does a standard pregnancy last?

Lot of people use this pregnancy calculator to determine their due date by counting forty weeks starting from the first day of their LMP.

Typically, forty weeks adds up to the following:

9 calendar months (30 or 31 days each)


10 lunar months (28 days each)

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