From the very moment that you announce to the world that you are going to have a baby the most asked question is “When are you due?”

Women have come a long way in being able to tell their due date, that is, as best as possible. Pregnant women in earlier times could only indicate they were due “around Thanksgiving” or “late fall”. But as health care becomes more of a priority, births are done less in the home and more in a hospital, making it necessary to be more accurate about when to be confined to a hospital bed. At this time it would be termed “estimated date of confinement”. Since then, science and technology have increased tremendously to make the prediction of a due date more accurate and we move to “expected date of delivery”, and to an even closer to sure date, the “due date.” But even now, making an accurate prediction is elusive because baby usually arrives on a due date less than 10% of the time.

Due Date Estimation

So what is the due date? This is an estimated date when the baby is expected to be born. The date is estimated because it is not so easy to tell when conception takes place in one woman to another. Every woman’s body is made up differently and circumstances and situations vary from one person to another. Human gestation (the period from conception to birth) is 38 weeks or 280 days. However, only a very few mothers know when they conceived, and since the circumstance around conception is not controlled it is not easy to tell. In one circumstance the egg of the woman may be ready just at the time when the sperm comes along and conception takes place. In another situation the sperm may linger in the fallopian tube until it meets the egg and in this instance conception is delayed.

The due date has to be estimated also because the baby’s arrival is dependent on the time you had your last period. Many women are not able to recall accurately when they had their period and can only guess. Furthermore, using the event of your last period is based upon a 28 day cycle which gives a more precise due date. A longer or shorter cycle is going to be cause for a more unsure date.

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Due Date Calculation

After you’ve found out that you are pregnant, your first order of business is to calculate your due date or estimated date of delivery (EDD). This is done in one of two ways. The average pregnancy lasts a total of 40 weeks or 38 weeks from when conception takes place. It is simple therefore to estimate when you are due by calculating exactly 40 weeks from the first day of your last menstrual period (LMP). These 40 weeks include the two weeks before conception takes place in women who have regular menstrual cycle. You could estimate the due date also using the Naegele’s Rule. Using the 280 days gestation period for babies, count back 3 months from the first day of your last menstrual period. Count back 7 more days from this date. The due date is estimated to be that date in the next year  .

Note that in both calculations it is only an estimated due date. Your baby could arrive two weeks later or sooner. You see, a baby’s due date is dependent on whether the mother was right about the date of her last period, the menstrual cycle which could be short or long, and the actual time of conception. The irregular period can be a real put off. Just imagine a woman has a five-week, six-week or seven-week cycle. In such circumstance it can be pretty hard to tell when conception had likely taken place. You will have to sit with your doctor and do some recall and estimation to come up with an estimated due date. You will be more unsure than the person who has a more predictable cycle. You will also want to put in the mix when baby himself is ready to come out.

Other Methods to Determine Due Date

In most mothers, the baby’s heartbeat can be heard at 10 – 12 weeks of the gestation period. The Doppler ultrasound can pick up the sound of the heartbeat at this age and this method is used to estimate the due date. Some experts do not recommend that you become dependent on the sonography technology to try to pinpoint a due date unless you are not sure of your last menstrual period.  It is felt that all fetal growth is the same up to 13 weeks. However, as the pregnancy progresses fetal growth changes and size may become unstable as you go along. Studies have suggested that although ultrasound is better in estimating due date, there is only a marginal difference between it and use of menstrual period information. In another study however, ultrasound is more accurate has indicated that there is no advantage in using menstrual period information if ultrasound results are available.

A pelvic examination done by your health care provider in the first trimester is a good way also to estimate the due date. If you are able to say accurately the date you last had your period, this along with a good examination by your doctor will more likely help you determine a reliable date. There is also the option of testing when hCG appears in the blood or urine. The hormone human chorionic gonadotropin (hCG) can be identified as early as 6 – 14 days or 3 – 4 weeks after fertilization. Once you have done your pregnancy test, you will almost be certain that the hormone will be present and you can judge the date when you will have your baby.

From the moment pregnancy has occurred, the aim is to be able to say when a baby is due and the mother and everyone else looks earnestly for when he or she will arrive. Due date is however an estimated date because none of the methods used to determine this is totally accurate. One thing is sure, only baby knows the date when he will arrive.