Once you’re pregnant, you will be very eager to know due date. Anyway calculating the pregnancy due date is not a very complicated task. There are several easy methods to calculate estimated due date. But it is a known fact that babies follow their own timetables and don’t arrive on your estimated due date.

Since exact date of the conception is seldom known, date of your last period is normally used to calculate when the baby is due. The due date is generally 40 weeks after the first day of your last menstrual period.

Another way to calculate your pregnancy due date is from conception, if it is known. Ovulation and conception normally occur after two weeks from the first day of last menstrual period. So the pregnancy due date will be 38 weeks from conception.

Ultrasound will be probably the accurate way to confirm your baby’s gestational age i.e. the age of the developing baby. It is the best method to calculate the due date by confirming one of the above methods. It helps in measuring the baby and these measurements help to calculate gestational age. It is a non-invasive test and can be performed as early as 5-6 weeks after your last menstrual period.

The most accurate results can be obtained using ultrasound between 8-18 weeks from beginning of the last menstrual period. The results of the ultrasound along with the calculated date from first day of your last period provide a relatively firm pregnancy due date.

For women whose periods are irregular the first day of the last period or conception methods cannot provide proper due date. So they usually must rely on ultrasound examination. If the baby is unusually large or small, the ultrasound test may also be unable provide the sufficient information to estimate the due date.