After finding out that you are pregnant the first question to go through your mind is usually, "How many weeks am I pregnant?" The answer to this question should be simple. There are two ways to calculate how far along you are; this article will explain both methods; you can choose which works best for you. Keep in mind no method can tell you exactly when your baby will be born, unless you are having a scheduled, medically assisted delivery.

Using Menstrual Cycles to Calculate

The oldest method of calculating the number of weeks pregnant a woman is throughout the pregnancy is the menstrual cycles. Before it was known that you had to ovulate to become pregnant it was commonly known that babies were born about 40 weeks after the last menstrual cycle. Since most women know when the first day of their last menstrual cycle was that was the date used to calculate how far along the pregnancy has progressed.

Using this method count from the first day of your last menstrual cycle (period) to the current date, this is how far along you are in weeks. If you want to have your due date then you can count the same way, 40 weeks is your expected due date.

Common sense tells you that you aren't actually pregnant before conception, but this method counts from the first day of your last period so on the day of conception you are approximately 2 weeks pregnant. This seems quite silly and confusing now that we understand the human reproductive system better. Because of this another way of answering the age old question "how many weeks am I pregnant" has been developed.

Day of Ovulation or Conception

The other method that is now used counts from the day of ovulation or day of conception, these dates may vary by two or three days. Some women keep track of their ovulation schedule and can tell when they ovulate; others are using the date that the doctor gives them from his estimate by ultrasound or other tests. This method uses the actual date of ovulation or the date of conception if known.

Counting from this date you start at week 0 and a week later instead of being 3 weeks pregnant you are 1 week pregnant. This makes more sense in the long run but can cause other confusion. When you end the first trimester of pregnancy with this method you are 10 weeks pregnant instead of 12 weeks. Your due date is not on week 40 with this method but week 38.

Both methods are counting to the same week; both methods have the same break down for trimesters. The reason you should know both methods is your doctor tells you that you are 10 weeks pregnant and you don't know which method he is using it is difficult to tell if you are at the end of the first trimester or if you still have a couple weeks. You can miscalculate due date by a full 2 weeks if you begin using one method and end using the other.

There is one more way to calculate your due date. This method was created to decrease the amount of counting you have to do although it has been caused a huge amount of confusion in women over the years. Use the first date of your last period, add seven days and subtract three months to get your babies expected due date. This method doesn't answer the question, 'how many weeks am I pregnant?' but it does tell you when to expect your baby and that is what is important.