How To Calculate Due Date?

For a woman who is pregnant, there are lots of information that play important roles in how the pregnancy progresses. One such thing that you might be informed about during your very first appointment with the doctor after your pregnancy confirmation is your expected due date. You would see this on your pregnancy and medical book/chart as EDD. EDD stands for expected due date and is calculated usually based on your last menstrual cycle date and also at times looking at the growth of the baby and how many weeks into pregnancy you are. Being informed helps us in various ways. Read on to know more about your due date and the significances associated with its calculation.

  • Gestation Period For Humans
  • Importance Of Tracking Ovulation
  • Calculating Your Due Date
  • Why The EDD Dating System Sometimes Does Not Work?
  • Is It Possible That The Due Date Could Change?
due date calculator week by week

Gestation Period For Humans

Pregnancy is also sometimes referred to as gestation. This period is the time when one or multiple offsprings develop inside a woman. Multiple pregnancies indicate more than one baby - twins, triplets, etc. When understanding the gestation period, we need to be aware of the last menstrual period, which is usually referred to as LMP. The gestation period is 40 weeks from this LMP. This would be just over 9 months. If calculated from the time of fertilization, then it would be 38 weeks. During the first eight weeks, post-fertilization, the term used for the developing offspring is the embryo. After the initial eight weeks, the offspring is referred to as the fetus until the remaining pregnancy term.

Importance Of Tracking Ovulation

If you are one of those who likes to stay informed about the biological process in the human body, then you would surely be monitoring your menstrual cycle as well. The onset of periods is actually based on when you ovulate. Even whether you conceive or not is also based on how well you ovulate. For a woman trying to conceive, keeping track of the ovulation could play an important role in successfully conceiving.

Ovulation is a process that could take 5 to 8 days. A woman's body contains estrogen and progesterone (pregnancy hormones). The ovulation cycle is dependent on our overall health and the balance of hormones in the body. Issues with pregnancy hormones could create problems when trying to conceive.

Tracking ovulation is also effective in avoiding unplanned pregnancies. You are most fertile during ovulation. Avoiding intercourse or taking necessary precaution during this period can help you prevent an unplanned pregnancy. Ovulation tracking has also been found effective in preventing ectopic pregnancy.

Calculating Your Due Date

The due date is mathematically calculated by subtracting 3 months from the first day of your LMP and then adding 7 days to this date. This is only a medical estimate. Your baby could be born anytime post 37 weeks, sometimes 38 weeks, naturally. The reason is that pregnancy is calculated from two weeks before you actually conceive (that is from the time a new menstrual cycle had begun for the month you conceived).

Research has shown that hardly only about 1 in 20 babies are actually born on the given due date. This is so because a normal and healthy pregnancy could range anywhere between 38 weeks to 42 weeks.

Why The EDD Dating System Sometimes Does Not Work?

For a woman who has a regular menstrual cycle, the pregnancy calendar would work almost correct most of the time. However, if the menstrual cycle happens to be irregular, then tracking when you actually conceived and when your LMP was could be complicated. Say if you get your periods every six or seven weeks, or such that you have not got your periods for the last three months and you take a pregnancy test randomly and see that the result is positive - the question now is 'When did you conceive?'

Answering this would be quite tricky as you wouldn't be sure as to when you ovulated due to the irregular menstrual cycle. However, there could be other clues to identify your EDD, which your healthcare practitioner would prefer, even if your LMP does not give an accurate date.

The clues that can help your practitioner determine your EDD are:

Size of your uterus: This is noted when you undergo the first internal pregnancy scan/examination.

Early ultrasound: This is effective in understanding the stage/status of your pregnancy. However, an early ultrasound may not work out for some women. Most practitioners will recommend this when you have irregular periods, to accurately identify when you would have possibly conceived. At times your age, such as being over 35 years, along with the history of pregnancy complications/miscarriages could also be the reason why an early ultrasound might have been prescribed.

Pregnancy milestones: This could help in determining the EDD. Milestones such as the first time the fetal heartbeat is heard could be one of them - this would usually occur at 9th to 12th week of pregnancy. Your fetal movement for the first time is also a milestone that usually occurs between 16 to 22 weeks. These milestones work as clues to determine if the identified EDD is accurate.

The fundal height: The top of your uterus would be measured by your practitioner each time you visit for a checkup. At about 20 weeks, your fundus should have reached your navel. This also helps in confirming the EDD.

Is It Possible That The Due Date Could Change?

Yes, there are chances that your due date could change. Although this is not a reason that should worry you, there are various factors why your doctor might change your EDD. If your periods are irregular and your early ultrasound dating was off, then it could change your EDD. Reasons such as first ultrasound happening during the second trimester, abnormality of the fundal height, abnormal levels of a protein called alpha-fetoprotein that is made by the baby are some of the reasons that could alter the EDD.

A healthy baby is assured if you pay good attention to the signs of your body that might indicate any form of health abnormalities. Good prenatal care is essential such that both the mother and baby are healthy both during pregnancy and after delivery.

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