Once you’ve discovered you’re pregnant, the first question that most easily pops out is, “When will I give birth?”. Knowing you are pregnant after so many months or even years of waiting not only makes you undeniably happy, but impatient as well. You begin to look forward to that day when you will finally be able to hold your baby in your arms.  Now, with a bit of arithmetic, you can determine the exact date of when that day will come.

EDC or estimated date of confinement is the term obstetricians use in referring to the time period when the woman is expected to have labor, give birth and confined to bed afterwards.

Term is that point when the baby is said to be fully mature and the gestational process has reached its peak. This usually happens at around the 38th -42nd week of pregnancy.  When we say that the baby is full-term, delivery is expected anytime soon within this time period. Within this four-week period, you will start to anticipate labor pains that signal the start of a long, arduous yet fulfilling task of giving birth.

Menstrual Cycle and Pregnancy

The woman’s body begins to prepare itself for ovulation on every first day of the menstrual cycle. Since having menses is the only visible outward sign that the reproductive organs of the female are working, this becomes the basis for counting the days of each cycle. Typically, a normal cycle lasts only up to 28 days.

Within these days, a lot of changes happen. As the uterus begins to prepare itself for fertilization (on the fist day of the cycle which is also the first day of menses), the uterine lining begins to thicken in preparation. As the days approach toward mid-cycle, a mature ovum is released by the ovaries in a process called ovulation. This signals the most fertile time in a woman’s cycle. Here, the egg waits for sperm to fertilize it and lead to conception.

The egg is only able to survive for 24-48 hours inside the uterus, and in cases when fertilization doesn’t occur, the endometrial lining sloughs off and menstruation occurs. When this happens, the start of another cycle begins.

When pregnancy does happen though, this is where the excitement really begins.

Doing the Math

By the time you discover you are pregnant because you missed a period, you will have been pregnant for roughly two weeks. However, for a more accurate counting, obstetricians usually ask you for you’re the date of the first day of your last menstrual period. This is the last cycle that you were able to ovulate and got pregnant.

Knowing the date of your last period helps you to count three months backwards in order to get the estimated day of confinement. The formula is given as follows:

Last menstrual period – 3 months + 7 days = EDC

For example, your last menstrual period was on August 16. Counting three months backwards will give you the month of May, and adding 7 days to that will end up in having May 13 as your EDC.7 days is added because this represents the time between that last menstrual cycle and the time between ovulation.

The reason why we use weeks instead of months in calculating the EDC is to provide more accurate and more detailed explanation of difficulties. This is also because gestational age of the fetus is calculated in weeks, with each week representing a milestone in the life of the fetus.  And this is how a natural pregnancy calculator works.

Is this method foolproof?

In reality, only a few women actually give birth on their due dates. This is because no one can be exactly sure when conception indeed took place. Unless if it is done through assisted reproductive technologies, then this EDC provides only a rough estimate. Usually an allowance of two weeks prior or two weeks after this date is considered to be your EDC.

About 80% of expectant mothers give birth to full-term babies and the remaining 20% deliver either prematurely or postmaturely.

Advantages of Knowing Your EDC

Sure, you will be able to pace your schedule and know when to start painting the nursery once you know when you are due, but there is a lot more to that as well.

Premature labor may happen even to the healthiest of pregnancies and this may be due to a number of factors which can include accidents or falls. This may threaten the fetus and when not managed immediately, premature delivery may occur. This is a serious threat to the life of the baby, as premature deaths remain the most common cause of mortality in newborns.

Post-term pregnancy on the other hand, provides more threat to the life of the fetus than to the mother. This is because as the placenta ages, it becomes less effective in delivering oxygen and nutrients to the fetus. When this happens, the health of the fetus is compromised.

By knowing your EDC, you can take measures to plan ahead on how you would approach your pregnancy in a healthy and safe way.  When you are past due date, your OB may also help induce labor if indicated.

For all these reasons, there is absolutely no excuse why should not use a pregnancy calculator and find out when you are due. Through this, you will be able to safeguard the health of your baby, as you anticipate his coming out to the world.