The length of pregnancy is 280 days or 40 weeks and the counting starts with the first day of your last menstrual period. The fact is it begins two weeks before you have got pregnant. That means the due date is calculated by your last period. This may not be as accurate as you think because the time of ovulation varies. If your menstrual cycle is 20 days, you ovulate on day 10. If it is 30 days, you ovulate on day 16. Doctors usually use all the information you give and finally make a calculated prediction.

  Use the pregnancy due date calculator to determine your expected date of delivery.

The predicted due date can be late or early. In the first case, the birth happens earlier than it is expected and the in the second, you might think the birth is overdue. The issue here is early labor induction can cause serious problems. It is found that having the ultrasound scan in the first three months of pregnancy can help your health care provider to pinpoint the due date accurately. On the other hand waiting for till the second trimester can lead to unnecessary interventions due to inaccurate due date. Having the ultra sound scan early and the doctor making prediction accurately can have the advantage of avoiding unnecessarily induced labor.

Induced labor may lead to birth defects such as low mental capacity and growth problems, you are always advised to go for the ultra sound scan in the first six to ten weeks of pregnancy. There are several factors affecting the prediction of the due date, whatever be the method you use. In a nut shell, having the ultrasound scan early can avoid the complications that might crop up later.